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84-480: It mounted six 106 mm manually loaded M40 recoilless rifles as its main armament, which could be fired in rapid succession against single targets to increase the probability of a kill. Although the actual caliber of the main guns was 105 mm, it was designated 106 mm to prevent confusion with the ammunition for the 105 mm M27 recoilless rifle, which the M40 replaced. It was produced in limited numbers for

168-589: A 10-day state visit to the US . President Eisenhower pledged his continued support, and a parade was held in Diệm's honor. But Secretary of State Dulles privately conceded Diệm had to be backed because they could find no better alternative. Between 1954 and 1957, the Diệm government succeeded in preventing large-scale organized unrest in the countryside. In April 1957, insurgents launched an assassination campaign, referred to as "extermination of traitors". 17 people were killed in

252-669: A Marxist–Leninist political organization which operated primarily in Hong Kong and the Soviet Union . The party aimed to overthrow French rule and establish an independent communist state in Vietnam. In September 1940, Japan invaded French Indochina, following France's capitulation to Nazi Germany . French influence was suppressed by the Japanese, and in 1941 Cung, now known as Ho Chi Minh , returned to Vietnam to establish

336-625: A Military Assistance and Advisory Group (MAAG) to screen French requests for aid, advise on strategy, and train Vietnamese soldiers. By 1954, the US had spent $ 1 billion in support of the French military effort, shouldering 80% of the cost of the war. During the Battle of Dien Bien Phu in 1954, US carriers sailed to the Gulf of Tonkin and the US conducted reconnaissance flights. France and

420-565: A psychological warfare campaign which exaggerated anti-Catholic sentiment among the Viet Minh and distributed propaganda attributed to Viet Minh threatening an American attack on Hanoi with atomic bombs. During the 300-day period, up to one million northerners, mainly minority Catholics, moved south, fearing persecution by the Communists. The exodus was coordinated by a U.S.-funded $ 93 million relocation program, which involved

504-471: A ceasefire with the Viet Minh, and independence was granted to Cambodia, Laos, and Vietnam. At the 1954 Geneva Conference, Vietnam was temporarily partitioned at the 17th parallel . Ho Chi Minh wished to continue war in the south, but was restrained by Chinese allies who convinced him he could win control by electoral means. Under the Geneva Accords, civilians were allowed to move freely between

588-646: A coordinated uprising in South Vietnam against the government and a third of the population was soon living in areas of communist control. In December 1960, North Vietnam formally created the Viet Cong (VC) with the intent of uniting all anti-GVN insurgents, including non-communists. It was formed in Memot, Cambodia , and directed through COSVN. The VC "placed heavy emphasis on the withdrawal of American advisors and influence, on land reform and liberalization of

672-561: A few were kept in service with safety barriers to protect the gunners, who fired the guns remotely. In December 2002, two M40s at Mammoth Mountain were destroyed by catastrophic bore explosions 13 days apart. The gunners were uninjured, having been protected by the safety barriers, but the incidents prompted the USFS to retire all remaining M40s in July 2003. Also in the mid-1990s, Parks Canada acquired four M40s for avalanche control to replace

756-520: A more "modest" winning margin of "60 to 70 percent." Diệm, however, viewed the election as a test of authority. He declared South Vietnam to be an independent state under the name Republic of Vietnam (ROV), with him as president. Likewise, Ho Chi Minh and other communists won at least 99% of the vote in North Vietnamese "elections". The domino theory , which argued that if a country fell to communism, all surrounding countries would follow,

840-557: A person knowledgeable in Indochinese affairs who did not agree that had elections been held as of the time of the fighting, possibly 80% of the population would have voted for the Communist Ho Chi Minh as their leader rather than Chief of State Bảo Đại. Indeed, the lack of leadership and drive on the part of Bảo Đại was a factor in the feeling prevalent among Vietnamese that they had nothing to fight for. According to

924-468: A policy of " Vietnamization " from 1969, which saw the conflict fought by an expanded ARVN, while US forces withdrew. A 1970 coup in Cambodia resulted in a PAVN invasion and a US–ARVN counter-invasion , escalating its civil war. US troops had mostly withdrawn from Vietnam by 1972, and the 1973 Paris Peace Accords saw the rest leave. The accords were broken almost immediately and fighting continued until

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1008-572: A purely tactical reason—to conceal the vulnerable M40 and its crew from the enemy until the main rifle was ready to fire. However, this restriction is believed to be the source of a long-standing misconception that the laws of war restrict the use of .50-caliber projectiles against enemy personnel more generally. In the early 1990s, the United States Forest Service (USFS) introduced the M40 for avalanche control as ammunition stocks for its M27 rifles became depleted. The M40

1092-816: A single target to guarantee a kill. The M40 could also be used on the M274 4×4 utility platform "mechanical mule." Replacing the M27 recoilless rifle , the M40 primarily saw action during the Vietnam War and was widely used during various conflicts thereafter in Africa or in the Middle East. It was replaced by the BGM-71 TOW anti-tank missile system in the US Armed Forces. The earlier M27 recoilless rifle

1176-632: A two-wheeled mount for the M40. The whole mounting can be placed on an M151 Jeep for mobile use. It has also been mounted on M113s , UMM 4x4s , Jongas , Fath Safirs , Land Rover Defenders , Mercedes-Benz G-Wagen , Hotchkiss M201 jeeps, Toyota Land Cruisers , Jeep CJs , Willys M38s , HMMWVs , M274 Mechanical Mules , Tiuna 106 mm weapons platforms , JODDB (formerly King Abdullah II Design and Development Bureau) Al Jawad vehicles, RBY MK 1s , AIL Abirs and AIL Storms . They were also used on US Navy minesweepers (MSO) during Operation Market Time in Vietnam. A special vehicle called

1260-506: Is a portable, crew-served 105 mm recoilless rifle made in the United States . Intended primarily as an anti-tank weapon , it could also be employed in an antipersonnel role with the use of an antipersonnel-tracer flechette round . The bore was commonly described as being 106 mm caliber but is in fact 105 mm; the 106 mm designation was intended to prevent confusion with incompatible 105 mm ammunition from

1344-663: Is the most commonly used title in English . It has been called the Second Indochina War since it spread to Laos and Cambodia , the Vietnam Conflict , and Nam (colloquially 'Nam). In Vietnam it is commonly known as Kháng chiến chống Mỹ ( lit.   ' Resistance War against America ' ). The Government of Vietnam officially refers to it as the Resistance War against America to Save

1428-526: The 1975 spring offensive and fall of Saigon to the PAVN, marking the war's end. North and South Vietnam were reunified in 1976. The war exacted enormous human cost : estimates of Vietnamese soldiers and civilians killed range from 970,000 to 3 million. Some 275,000–310,000 Cambodians , 20,000–62,000 Laotians , and 58,220 US service members died. Its end would precipitate the Vietnamese boat people and

1512-1383: The Canadian Armed Forces using 105 mm towed howitzers in Rogers Pass (British Columbia) on the Trans-Canada Highway. Special pedestals were built at specific locations and a pneumatic remote firing system was devised to allow the operators to fire the recoilless rifle safely in case of ammunition malfunction. After a trial period, the M40s plan was abandoned and the Canadian Armed Forces once again began providing 105 mm towed howitzers and artillery personnel to conduct avalanche control. Vietnam War ≈860,000 (1967) ≈1,420,000 (1968) Total military dead/missing: ≈1,100,000 Total military wounded: ≈604,200 (excluding GRUNK / Khmer Rouge and Pathet Lao ) Second Third American intervention 1965 1966 1967 Tet Offensive and aftermath Vietnamization 1969–1971 1972 Post- Paris Peace Accords (1973–1974) Spring 1975 Air operations Naval operations Lists of allied operations The Vietnam War (1 November 1955 – 30 April 1975)

1596-559: The Châu Đốc massacre at a bar in July, and in September a district chief was killed with his family. By early 1959, Diệm had come to regard the violence as an organized campaign and implemented Law 10/59, which made political violence punishable by death and property confiscation. There had been division among former Viet Minh, whose main goal was to hold elections promised in the Geneva Accords, leading to " wildcat " activities separate from

1680-669: The Cold War between the Soviet Union and US. American military involvement greatly escalated from 1965 until its withdrawal in 1973. The fighting spilled over into the Laotian and Cambodian Civil Wars , which ended with all three countries becoming communist in 1975. After the defeat of French Indochina in the First Indochina War that began in 1946, Vietnam gained independence in the 1954 Geneva Conference but

1764-808: The Cuban Missile Crisis (October 1962) played out on television worldwide. It was the closest the Cold War came to nuclear war . The Kennedy administration remained committed to the Cold War foreign policy inherited from the Truman and Eisenhower administrations. In 1961, the US had 50,000 troops based in South Korea, and Kennedy faced four crisis situations: the failure of the Bay of Pigs Invasion he had approved in April, settlement negotiations between

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1848-569: The French Navy and the US Seventh Fleet to ferry refugees. The northern refugees gave the later Ngô Đình Diệm regime a strong anti-communist constituency. Over 100,000 Viet Minh fighters went to the north for "regroupment", expecting to return south within two years. The Viet Minh left roughly 5,000 to 10,000 cadres in the south as a base for future insurgency. The last French soldiers left South Vietnam in April 1956 and

1932-669: The Ho Chi Minh trail to supply and reinforce the VC. By 1963, the north had covertly sent 40,000 soldiers of its own People's Army of Vietnam (PAVN), armed with Soviet and Chinese weapons, to fight in the insurgency in the south. President John F. Kennedy increased US involvement from 900 military advisors in 1960 to 16,300 in 1963 and sent more aid to the Army of the Republic of Vietnam (ARVN), which failed to produce results. In 1963, Diem

2016-660: The Korean War in June convinced Washington policymakers that the war in Indochina was another example of communist expansionism, directed by the Soviet Union. Military advisors from China began assisting the Viet Minh in July 1950. Chinese weapons, expertise, and laborers transformed the Viet Minh from a guerrilla force into a regular army. In September 1950, the US further enforced the Truman Doctrine by creating

2100-810: The Ontos carried six M40s. A version specific to the T195E5 mount, the M40A1C, was used. It was used only by the U.S. Marine Corps . Some Pakistani M113s have a dual mounting. Three Panagopoulos coastal patrol boats class of the Hellenic Coast Guard and the Hellenic Navy in service of 1976-2003 was armed with two sextuples M40. The M40 was a very successful export item and continues to be used by South Korea , Ecuador , Estonia , Greece , Honduras , Iran , Lebanon , Malaysia , Mexico , Morocco ,

2184-628: The Pentagon Papers , which commented on Eisenhower's observation, Diệm would have been a more popular candidate than Bảo Đại against Hồ, stating that "It is almost certain that by 1956 the proportion which might have voted for Ho - in a free election against Diem - would have been much smaller than 80%." In 1957, independent observers from India, Poland, and Canada representing the International Control Commission (ICC) stated that fair elections were impossible, with

2268-574: The Philippines , Taiwan , Turkey , Colombia , Venezuela and many others, as well as anti-government forces in the Libyan Civil War and Syrian civil war . Ammunition for the 105 mm rifle was issued as one-piece fixed cartridges. The term "fixed" means that the projectile and the cartridge case are crimped together. This ensures correct alignment of the projectile and the cartridge case . It also permits faster loading because

2352-463: The U.S. Marines after the U.S. Army cancelled the project. The Marines consistently reported excellent results when they used the Ontos for direct fire support against infantry in numerous battles and operations during the Vietnam War . The American stock of Ontos was largely expended towards the end of the conflict and the Ontos was removed from service in 1969. The Ontos (Greek for "thing") project

2436-601: The Viet Minh , an anti-Japanese resistance movement that advocated for independence. The Viet Minh received aid from the Allies , namely the US, Soviet Union, and Republic of China . Beginning in 1944, the US Office of Strategic Services (O.S.S.) provided the Viet Minh with weapons, ammunition, and training to fight the occupying Japanese and Vichy French forces. Throughout the war, Vietnamese guerrilla resistance against

2520-597: The 297 vehicles initially accepted by the Marines, only 176 were converted between 1963 and 1965 to this standard. A mockup was built of an Ontos chassis with a Maxson M45 quadmount .50 BMG antiaircraft mount. While the M50 was designed as a tank destroyer, during the Vietnam War most M50s did not engage enemy armor as the North Vietnamese Army deployed few tanks. The Ontos was therefore more widely used by

2604-614: The American involvement in the Dominican Civil War : on 29 April 1965 an M50 Ontos and an M48 Patton of the 6th MEU engaged and destroyed two rebel L/60L light tanks, each destroying one. In another instance, an Ontos destroyed an AMX-13 . Of the 297 built, only 14 remain, many of which are the M50A1 model. There are Ontos on display at the following US locations: M40 recoilless rifle The M40 recoilless rifle

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2688-524: The British were opposed. Eisenhower, wary of involving the US in an Asian land war, decided against intervention. Throughout the conflict, US intelligence estimates remained skeptical of France's chance of success. On 7 May 1954, the French garrison at Dien Bien Phu surrendered. The defeat marked the end of French military involvement in Indochina. At the Geneva Conference , they negotiated

2772-455: The GVN, on coalition government and the neutralization of Vietnam." The identities of the leaders of the organization were often kept secret. Support for the VC was driven by resentment of Diem's reversal of Viet Minh land reforms in the countryside. The Viet Minh had confiscated large private landholdings, reduced rents and debts, and leased communal lands, mostly to poorer peasants. Diem brought

2856-588: The ICC reporting that neither South nor North Vietnam had honored the armistice agreement. From April to June 1955, Diệm eliminated political opposition in the south by launching operations against religious groups: the Cao Đài and Hòa Hảo of Ba Cụt . The campaign also attacked the Bình Xuyên organized crime group, which was allied with members of the communist party secret police and had military elements. The group

2940-472: The Japanese grew dramatically, and by the end of 1944 the Viet Minh had grown to over 500,000 members. US President Franklin D. Roosevelt was an ardent supporter of Vietnamese resistance, and proposed that Vietnam's independence be granted under an international trusteeship following the war. Following the surrender of Japan in 1945, the Viet Minh launched the August Revolution , overthrowing

3024-677: The Japanese-backed Empire of Vietnam and seizing weapons from the surrendering Japanese forces. On September 2, Ho Chi Minh proclaimed the Declaration of independence of the Democratic Republic of Vietnam (DRV). However, on September 23, French forces overthrew the DRV and reinstated French rule. American support for the Viet Minh promptly ended, and O.S.S. forces left as the French sought to reassert control of

3108-558: The M368 dummy round which could not be fired and was used for crew drill. The original U.S. HEAT round penetrated more than 400 mm of armor. Near the end of the M40's service life, both Austria and Sweden produced HEAT rounds for the weapon capable of penetrating more than 700 mm of armor. The ammunition for the M8C spotting rifle is not .50 BMG , but a 22mm shorter (12.7x77mm) round than used in .50 caliber machine guns. The spotter round

3192-649: The Nation. It is sometimes called the American War . Vietnam had been under French control as part of French Indochina since the mid-19th century. Under French rule, Vietnamese nationalism was suppressed, so revolutionary groups conducted their activities abroad, particularly in France and China. One such nationalist, Nguyen Sinh Cung , established the Indochinese Communist Party in 1930,

3276-438: The Ontos was the only tracked vehicle light enough to cross a pontoon bridge. In the Battle of Huế , Colonel Stanley S. Hughes felt the Ontos was the most effective of all Marine supporting arms. At ranges of 300 to 500 yards (270 to 460 m), its recoilless rifles could knock holes in or completely knock down walls. The appearance of an Ontos was sometimes enough to make the enemy break and run, and anecdotal accounts describe

3360-409: The PRC also completed its withdrawal from North Vietnam. Between 1953 and 1956, the North Vietnamese government instituted agrarian reforms, including "rent reduction" and "land reform", which resulted in political oppression. During land reform, North Vietnamese witnesses suggested a ratio of one execution for every 160 village residents, which extrapolates to 100,000 executions. Because the campaign

3444-408: The State of Vietnam, with Bảo Đại as Emperor, and Ngô Đình Diệm as prime minister. Neither the US, nor Diệm's State of Vietnam, signed anything at the Geneva Conference. The non-communist Vietnamese delegation objected strenuously to any division of Vietnam, but lost when the French accepted the proposal of Viet Minh delegate Phạm Văn Đồng , who proposed Vietnam eventually be united by elections under

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3528-426: The US Marines for direct fire support for the infantry in combat, a role that was never emphasized in training or doctrine. Its light armor was effective against small arms but vulnerable to mines and rocket-propelled grenades . Consequently, many Ontos were deployed in static defense positions. The relatively light weight of the M50 made it exceptionally mobile for the amount of firepower it carried. In one operation,

3612-453: The US discussed the use of tactical nuclear weapons , though reports of how seriously this was considered and by whom, are vague. According to then-Vice President Richard Nixon , the Joint Chiefs of Staff drew up plans to use nuclear weapons to support the French. Nixon, a so-called " hawk ", suggested the US might have to "put American boys in". President Dwight D. Eisenhower made American participation contingent on British support, but

3696-406: The United States. The M40 is shaped like a long tube with an M8C .50 cal spotting rifle above. The spotting rifle fires a round whose trajectory closely matches that of the 105 mm round and gives off a puff of smoke on impact with the target. On the left side, there is an elevating wheel, in the center of which is the trigger wheel used to fine adjust the elevation and at the same time firing

3780-473: The Vienna summit with Khrushchev, "Now we have a problem making our power credible and Vietnam looks like the place." Kennedy's policy toward South Vietnam assumed Diệm and his forces had to defeat the guerrillas on their own. He was against the deployment of American combat troops and observed "to introduce U.S. forces in large numbers there today, while it might have an initially favorable military impact, would almost certainly lead to adverse political and, in

3864-743: The border. About 500 of the "regroupees" of 1954 were sent south on the trail during its first year of operation. The first arms delivery via the trail was completed in August 1959. In April 1960, North Vietnam imposed universal military conscription for men. About 40,000 communist soldiers infiltrated the south from 1961 to 1963. In the 1960 U.S. presidential election , Senator John F. Kennedy defeated incumbent Vice President Richard Nixon. Although Eisenhower warned Kennedy about Laos and Vietnam, Europe and Latin America "loomed larger than Asia on his sights." In June 1961, he bitterly disagreed with Soviet premier Nikita Khrushchev when they met in Vienna to discuss key U.S.–Soviet issues. Only 16 months later,

3948-438: The country . Tensions between the Viet Minh and French authorities had erupted into full-scale war by 1946, a conflict which soon became entwined with the wider Cold War . On March 12, 1947, US President Harry S. Truman announced the Truman Doctrine , an anticommunist foreign policy which pledged US support to nations resisting "attempted subjugation by armed minorities or by outside pressures". In Indochina, this doctrine

4032-438: The country to the Virgin Mary . In the summer of 1955, Diệm launched the "Denounce the Communists" campaign, during which suspected communists and other anti-government elements were arrested, imprisoned, tortured, or executed. He instituted the death penalty in August 1956 against activity deemed communist. The North Vietnamese government claimed that, by November 1957, over 65,000 individuals were imprisoned and 2,148 killed in

4116-418: The demilitarized zone, between North and South Vietnam. The North Vietnamese Communist Party approved a "people's war" on the South at a session in January 1959, and, in May, Group 559 was established to maintain and upgrade the Ho Chi Minh trail , at this time a six-month mountain trek through Laos. On 28 July, North Vietnamese and Pathet Lao forces invaded Laos, fighting the Royal Lao Army all along

4200-415: The end of 1965, and to 536,000 by the end of 1968. US forces relied on air supremacy and overwhelming firepower to conduct search and destroy operations in rural areas. In 1968, North Vietnam launched the Tet Offensive , which was a tactical defeat but convinced many in the US that the war could not be won. The PAVN began engaging in more conventional warfare . Johnson's successor, Richard Nixon , began

4284-400: The enemy fleeing occupied buildings when an Ontos's spotting round entered a window. In Operation Desoto , the introduction of the large CH-53 Sea Stallion helicopter made possible moving a platoon 25 miles (40 km) south of Quảng Ngãi City carrying Ontos in slings underneath the aircraft. The Ontos was taken out of service in 1969, and by 1970 were removed entirely from service. Some of

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4368-544: The failed M27. The air-cooled, breech-loaded , single-shot rifle fired fixed ammunition and was used primarily from a wheeled ground mount or M92 ground mount. It was designed for direct firing only, and sighting equipment for this purpose was furnished with each weapon, including an affixed M8C .50 cal spotting rifle . 297 M50 "Ontos" were built as self-propelled light armored tracked anti-tank vehicles. They had six 105 mm M40 recoilless rifles as their main armament, which could be fired in rapid succession against

4452-454: The insurgency entitled "The Road to the South" to the Politburo in Hanoi. However, as China and the Soviets opposed confrontation, his plan was rejected. Despite this, the North Vietnamese leadership approved tentative measures to revive southern insurgency in December 1956. Communist forces were under a single command structure set up in 1958. In May 1958, North Vietnamese forces seized the transportation hub at Tchepone in Southern Laos near

4536-402: The landlords back, people who had been farming land for years had to return it to landlords and pay years of back rent. Marilyn B. Young wrote that "The divisions within villages reproduced those that had existed against the French: 75% support for the NLF, 20% trying to remain neutral and 5% firmly pro-government". In March 1956, southern communist leader Lê Duẩn presented a plan to revive

4620-416: The larger Indochina refugee crisis , which saw millions leave Indochina, an estimated 250,000 perished at sea. The US destroyed 20% of South Vietnam's jungle and 20–50% of the mangrove forests, by spraying over 20 million U.S. gallons (75 million liters) of toxic herbicides; a notable example of ecocide . The Khmer Rouge carried out the Cambodian genocide , while conflict between them and

4704-420: The long run, adverse military consequences." The quality of the South Vietnamese military, however, remained poor. Poor leadership, corruption, and political promotions weakened the ARVN. The frequency of guerrilla attacks rose as the insurgency gathered steam. While Hanoi's support for the VC played a role, South Vietnamese governmental incompetence was at the core of the crisis. One major issue Kennedy raised

4788-446: The other communists and anti-GVN activists. Douglas Pike estimated that insurgents carried out 2,000 abductions, and 1,700 assassinations of government officials, village chiefs, hospital workers and teachers from 1957 to 1960. Violence between insurgents and government forces increased drastically from 180 clashes in January 1960, to 545 clashes in September. In September 1960, COSVN , North Vietnam's southern headquarters, ordered

4872-414: The pro-Western government of Laos and the Pathet Lao communist movement in May, construction of the Berlin Wall in August, and the Cuban Missile Crisis in October. Kennedy believed another failure to stop communist expansion would irreparably damage US credibility. He was determined to "draw a line in the sand" and prevent a communist victory in Vietnam. He told James Reston of The New York Times after

4956-412: The process. According to Gabriel Kolko , 40,000 political prisoners had been jailed by the end of 1958. In October 1956, Diệm launched a land reform program limiting the size of rice farms per owner. 1.8m acres of farm land became available for purchase by landless people. By 1960, the process had stalled because many of Diem's biggest supporters were large landowners. In May 1957, Diệm undertook

5040-455: The projectile and the cartridge case are loaded as one unit. The rear end of the cartridge case is perforated, to allow the propellant gas to escape through the vented breech, thus neutralizing recoil. Most projectiles (except HEAT) used are pre-engraved, that is, the rotating bands are cut to engage the rifled bore. Types of ammunition included HEAT , High Explosive Plastic- Tracer ( HEP-T ), canister , High Explosive Anti Personnel, and

5124-420: The spotting rifle when pulled, and the gun when pushed. The mounting is a tripod , but the front leg has a castering wheel. On top of the mount is a traverse wheel. On the center of the traverse wheel is a locking wheel, when the wheel is down, the rifle is locked in traverse, and can only be moved right and left with the traverse wheel. When the wheel is raised, the rifle can be traversed by hand. Austria produced

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5208-630: The supervision of "local commissions". The US countered with what became known as the "American Plan", with the support of South Vietnam and the UK. It provided for unification elections under the supervision of the UN, but was rejected by the Soviet delegation. The US said, "With respect to the statement made by the representative of the State of Vietnam, the United States reiterates its traditional position that peoples are entitled to determine their own future and that it will not join in any arrangement which would hinder this". US President Eisenhower wrote in 1954: I have never talked or corresponded with

5292-411: The target. The Ontos also carried a single .30 caliber (7.62 mm) M1919A4 machine gun for anti-infantry use. The vehicle was taken to the Aberdeen Proving Ground where single rifles had been tested earlier. When all six weapons were fired at once, the back blast from the firing knocked bricks out of a nearby building and knocked the rear windows out of several cars. The prototype and testing stage

5376-442: The two provisional states for a 300-day period. Elections throughout the country were to be held in 1956 to establish a unified government. However, the US, represented at the conference by Secretary of State John Foster Dulles , objected to the resolution; Dulles' objection was supported only by the representative of Bảo Đại. John Foster's brother, Allen Dulles , who was director of the Central Intelligence Agency , then initiated

5460-470: The unified Vietnam escalated into the Cambodian–Vietnamese War . In response, China invaded Vietnam , with border conflicts lasting until 1991. Within the US, the war gave rise to Vietnam syndrome , a public aversion to American overseas military involvement, which, with the Watergate scandal , contributed to the crisis of confidence that affected America throughout the 1970s. Various names have been applied and have shifted over time, though Vietnam War

5544-417: The vehicle due to limited space. Its most prominent armament was its six M40 recoilless rifles . Four of the recoilless rifles also had .50 BAT (12.7x77mm) M8C spotting rifles attached, each of which fired a tracer round with the same trajectory as the 105 mm round, and which gave off a flash and puff of white smoke on impact. The spotting rifles were used to line up the 105 mm recoilless rifles with

5628-527: The vehicles were handed over to an Army light infantry brigade. They used them until they ran out of spare parts, and then removed the turrets and used them as fixed fortifications. Both these and the rest of the vehicles returned from Vietnam in 1970 and were cut up for scrap, with some of the chassis being sold off to be converted into construction vehicles. Some of the Ontos that were sold to construction companies were later acquired by collectors for restoration. The Ontos did see use as an anti-tank weapon during

5712-399: Was a 105 mm weapon developed in the early 1950s and fielded in the Korean War . Although a recoilless rifle of this caliber had been a concept since the Second World War , the weapon was hurriedly produced with the onset of the Korean War. The speed with which it was developed and fielded resulted in problems with reliability caused by trunnions that were mounted too far to the rear. The M27

5796-412: Was a light Armored personnel carrier (APC), but only two versions of the prototype were built. It proved impractical due to the limited room inside, carrying only five infantry and forcing the driver to lie prone. A "stretched" version known as the Utility Vehicle, Tracked, Infantry, T56 was also built, and while it held a complete eight-man team, their equipment had to be carried on the outside. Neither

5880-432: Was also considered too heavy by the U.S. Army and had a disappointing effective range due to the lack of a spotting rifle. Taking the M27 as the basis for a new design, the Army developed an improved version of the M27 that was type-designated the M40 106-mm recoilless rifle in 1955. Although unsuitable for military purposes, M27 recoilless rifles were used to trigger controlled avalanches at ski resorts and mountain passes in

5964-417: Was an armed conflict in Vietnam , Laos , and Cambodia fought between North Vietnam (Democratic Republic of Vietnam) and South Vietnam (Republic of Vietnam) and their allies. North Vietnam was supported by the Soviet Union and China , while South Vietnam was supported by the United States and other anti-communist nations. The conflict was the second of the Indochina Wars and a major proxy war of

6048-467: Was based on the running gear of the M56 Scorpion light anti-tank vehicle. The vehicle mounted a cast steel turret with two arms holding three rifles each. This early model could traverse the turret only about 15 degrees. A second prototype used a new suspension system, new tracks, and a newer turret with about 40 degrees traverse. The vehicle could carry only eighteen rounds for the main guns inside

6132-739: Was completed by 1955, at which point the Army canceled its order. As an anti-tank vehicle the Ontos had several problems, including a small ammunition load, a very high profile for such a small vehicle, and the need for the crew to exit the vehicle in order to reload the guns, exposing them to enemy fire. Although the Army had canceled its order, the Marine Corps was desperate for any anti-tank vehicles it could get, and ordered 297. Production ran from 1955 through 1957. The Marine Corps accepted its first vehicle on 31 October 1956. Several variants were also studied. The Utility Vehicle, Tracked, Infantry, T55

6216-509: Was considered very useful. In 1960 there was a brief study made to replace the Ontos's 106 mm rifles with a new 105 mm design that included a revolver -style autoloader . This project was not accepted. Another proposed upgrade was replacing the GMC engine with a newer Chrysler 361 cu in (5.92 L) V8 engine. This upgrade was implemented and the variant was named Rifle, Multiple 106 mm, Self-propelled, M50A1 . However, of

6300-528: Was created to be an air transportable tank destroyer capable of being lifted by the cargo aircraft of the 1950s. This limited the vehicle to a weight between 10 and 20 metric tons . The Ontos also had to use the six-cylinder engine then widely used in the Army's GMC trucks. After a number of design and engineering meetings from March through October 1951, manufacturer Allis-Chalmers was awarded an initial contract to produce 14 pilot vehicles, encompassing 6 variants. Allis-Chalmers' first vehicle, completed in 1952,

6384-562: Was defeated in April following a battle in Saigon . As broad-based opposition to his harsh tactics mounted, Diệm increasingly sought to blame the communists. In a referendum on the future of the State of Vietnam in October 1955, Diệm rigged the poll supervised by his brother Ngô Đình Nhu and was credited with 98% of the vote, including 133% in Saigon. His American advisors had recommended

6468-561: Was developed to replicate the trajectory of the 106 mm ammunition, and features a tracer element and a point-detonating incendiary filler to create a puff of white smoke at the impact point. Four of the six 106mm rifles on the M50 Ontos mounted spotter rifles. Spotter rounds had a yellow tip with a red band and practice cartridges had a green tip. Although the spotting rifle could conceivably be used in an antipersonnel role, historic U.S. military doctrine strongly discouraged this use, for

6552-433: Was divided into two parts at the 17th parallel : the Viet Minh , led by Ho Chi Minh , took control of North Vietnam, while the US assumed financial and military support for South Vietnam, led by Ngo Dinh Diem . The North Vietnamese began supplying and directing the Viet Cong (VC), a common front of dissidents in the south, which intensified a guerrilla war from 1957. In 1958, North Vietnam invaded Laos , establishing

6636-888: Was first proposed by the Eisenhower administration . John F. Kennedy , then a senator , said in a speech to the American Friends of Vietnam : "Burma, Thailand, India, Japan, the Philippines and obviously Laos and Cambodia are among those whose security would be threatened if the Red Tide of Communism overflowed into Vietnam." A devout Roman Catholic, Diệm was fervently anti-communist, nationalist, and socially conservative. Historian Luu Doan Huynh notes "Diệm represented narrow and extremist nationalism coupled with autocracy and nepotism ." Most Vietnamese were Buddhist , and alarmed by Diệm's actions, like his dedication of

6720-746: Was first put into practice in February 1950, when the United States recognized the French-backed State of Vietnam in Saigon , led by former Emperor Bảo Đại, as the legitimate government of Vietnam, after the communist states of the Soviet Union and People's Republic of China recognized the Democratic Republic of Vietnam , led by Ho Chi Minh, as the legitimate Vietnamese government the previous month. The outbreak of

6804-440: Was initially successful due to operational similarities to the familiar M27 and ready availability from the U.S. military; however, in 1995, a USFS gunner was killed by shrapnel after a low-level premature warhead detonation inside an M40 barrel. The accident was attributed to an undiscovered hairline crack in the projectile's base plate. Following this incident, most USFS M40s were quickly replaced with surplus 105 mm howitzers , but

6888-474: Was killed in a US-backed military coup , which added to the south's instability. Following the Gulf of Tonkin incident in 1964, the US Congress passed a resolution that gave President Lyndon B. Johnson authority to increase military presence without a declaration of war. Johnson launched a bombing campaign of the north and began sending combat troops, dramatically increasing deployment to 184,000 by

6972-523: Was mainly in the Red River Delta area, 50,000 executions became accepted by scholars. However, declassified documents from Vietnamese and Hungarian archives indicate executions were much lower, though likely greater than 13,500. In 1956, leaders in Hanoi admitted to "excesses" in implementing this program and restored much of the land to the original owners. The south, meanwhile, constituted

7056-632: Was whether the Soviet space and missile programs had surpassed those of the US. Although Kennedy stressed long-range missile parity with the Soviets, he was interested in using special forces for counterinsurgency warfare in Third World countries threatened by communist insurgencies. Although they were intended for use behind front lines after a conventional Soviet invasion of Europe, Kennedy believed guerrilla tactics employed by special forces, such as

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