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Ontos M50 Motor Carriage, 106mm Recoilless Rifle

The Army began developing ONTOS (in Greek, "the thing") in March 1951. It was to be a relatively lightweight, full-track, highly mobile vehicle carrying a crew of two and armed with six 106 mm recoilless rifles mounted externally. Although agile, ONTOS did not have the capability for sustained action on the battlefield. It carried only eight 105 mm rounds in addition to those in the six gun tubes. Moreover, the vehicle had to withdraw to cover for protection during reloading. Normally, ONTOS would fight from ambush.

The advanced M40 106mm rifle (called BAT or battalion anti-tank weapon) to be carried by ONTOS had been in development since 1950 and was to be capable of knocking out the Soviets' heaviest tank, the JSIII (Joseph Stalin III). The BAT system employed spotting rounds from a .50 caliber rifle to make fire from the 106mm recoilless rifle more accurate. In addition to ONTOS, the Ordnance Corps was also designing an ordinary jeep carrier for BAT. The BAT was derived from the rather unsatisfactory M27 105mm Recoilless Rifle. To avoid confusion and to also prevent use of the M27 ammunition still in stocks in the new weapon, the M40 was classified as a "106mm" weapon.

During World War II, the Army had developed self-propelled tank destroyers on which were mounted effective antitank guns (3-inch, 76mm and 90mm) long before those guns were mounted on tanks. Yet widespread dissatisfaction with tank destroyer units resulted in their disbanding following the war. The Stilwell Board concluded, "The thin-skinned, self-propelled tank destroyer has too limited a role to warrant further development now that comparable gun power can be attained in tank development."

Early in 1951, the three services contracted with and participated in a study (Project VISTA), conducted by the California Institute of Technology, of the tactics, techniques, and equipment that might be employed to halt a Soviet attack across a wide front in Western Europe. One of the study's recommendations-to rush into production an anti-tank weapon then being developed by the Army-occasioned a conflict between Secretary of the Army Frank Pace and Army Chief of Staff J. Lawton Collins.

One of the VISTA recommendations the Army staff did not want to highlight concerned the ONTOS anti-tank weapon then being developed by the Ordnance Corps. The Caltech study urged the Army to freeze the system's design and to "initiate high priority procurement in sufficient numbers to meet the tank threat in Western Europe." Based on contacts with automotive industry representatives, the scientists believed 10,000 could be produced by mid-1952. The General Staff committee did not concur with these suggestions, maintaining that production should not begin until ONTOS had been fully field-tested.

Aside from the question of its readiness for production, some in the Army, first and foremost General Collins, were hostile to ONTOS because of its defensive orientation and potential to threaten the tank's primacy among the service's mechanized weapon systems. Secretary Pace, however, had been an early ONTOS supporter. In fact, in October 1951, several months before the VISTA group submitted its report, Pace had already directed the chief of staff to accelerate ONTOS development. That decision, now reinforced by the scientists' call to move quickly to production, brought the civilian secretary into conflict with the Army's top uniformed officer. The dispute involved not only the issue of the appropriate development pace for ONTOS but also, at least in Collins's mind, the future of the tank and the continued ascendancy of the offensive in the Army's doctrine.

Secretary Pace found the ONTOS particularly attractive because it promised to be much less expensive than the tank. Initial estimates were that the unit cost of the ONTOS would be $25,000-30,000; the M47 medium tank ran approximately $240,000 per copy. In early November 1951, Pace participated in a discussion of the tank's future in combat with several officers from the Army staff, including General J. E. Hull, the vice chief of staff. The secretary told the group that the Army must constantly evaluate the tank's vulnerability with respect to recoilless weapons. Moreover, tanks were increasing in weight at the same time raw materials had become more of a limiting factor in warfare (the Office of Defense Mobilization had instituted the Controlled Materials Plan in July). Stating that he hoped that ONTOS was being developed "on a crash basis," he reminded everyone present that "the public and Congress were constantly hoping for a cheaper, highly effective weapon in the armored field."

By mid-summer 1952, despite Secretary Pace's desire for rapid progress, ONTOS development was not far along. Only three pilot models had been manufactured (of the twelve to be constructed) and the system was only just entering the engineering test phase, the first step in the Army's formal and extensive evaluation process for new weapons and other equipment. The most optimistic estimate, assuming successful completion of all tests by January 1953, was that quantity production could start early in calendar year 1954.

In July 1952, General Matthew B. Ridgway, Eisenhower's successor as SACEUR, wrote General Collins asking if testing of ONTOS and BAT might be expedited to make them available more quickly, not to US forces but to NATO allies under the MDAP program. He believed the new anti-tank weapons would be necessary "to withstand the mass of Soviet armor which will inevitably be launched against us at the very outset of hostilities . . .." If possible, Ridgway wanted procurement orders to be placed before the end of FY 1953.

General Collins replied that he could not approve the request. For one thing, he did not think it wise to accept any weapon for the NATO partners without its being fully tested by the AFF or to put the system in the hands of foreign forces before its issue to US troops. Additionally, short-circuiting the acquisition cycle to initiate early production created problems:

"We have of necessity placed several combat vehicles in production without complete test and evaluation in the past. This has resulted in numerous changes in production and modification to vehicles already produced. While this has speeded our readiness considerably, the procedure has caused production difficulties and added costs. Furthermore, desired modifications are not always practical to incorporate into a vehicle already off the production line."

Thus, while Collins indicated that testing of the two anti-tank weapons might be hurried up some, he was opposed to starting production before the full evaluation process had run its course.

At this point Secretary Pace, who was then in Germany and had become aware of Collins' letter to Ridgway, intervened. In a terse telegram to the chief of staff on 8 August 1952, Pace declared: "Appreciate your taking no action to implement your letter to Ridgway concerning method of expediting ONTOS and BAT. Expect to participate in final decision myself." Pace told Lt. Gen. Maxwell Taylor, the deputy chief of staff for operations and administration who was accompanying him in Europe, that he wanted to be briefed on the pros and cons of telescoping the development, testing, and production of ONTOS and BAT when he returned to Washington.

The Army staff undertook the analysis Pace had requested and presented it to General Collins for approval before submitting it to the secretary. The staff's view was that engineering tests and service tests could take place simultaneously but that production should not begin until ONTOS and BAT had been accepted by the AFF. Collins concurred with the recommendations but also remarked that ONTOS was "a cheap tank destroyer, not a replacement for the tank. The infantry needs a tank to fight other infantry."

During the briefing for Secretary Pace on 4 September 1952, General Collins emphasized BAT's effectiveness as a tank killer and as one element in the array of the Army's tank-defeating weapons. Significantly, in this context Collins referred to BAT mounted on the jeep not on the ONTOS. Although acknowledging that that the number of tanks assigned to a division might be reduced, the chief of staff declared that it would not be because of the addition of ONTOS. Perhaps to Collins's surprise and relief, Pace conceded that the ONTOS would not replace the tank. Moreover, the secretary did not insist that production be initiated before testing was finished. Nonetheless, Pace reminded all those present just who was in charge by requiring that testing adhere strictly to the projected schedule and be concluded by January 1953 "or that an explanation satisfactory to him be given as to why the time should be extended."

On 9 January 1953, with less than two weeks to go in his term as Army secretary, Pace was brought up to date on the status of ONTOS and BAT. The news was not good. Testing over the past four months had revealed deficiencies in both that had not yet been corrected. The problems with BAT, however, were less serious and General Collins recommended that production begin even though more tests were needed before the AFF could accept the system for troop issue. On the other hand, the chief of staff did not advise starting ONTOS production until service tests were completed. Even then, he stated, the Army should procure only 300 for field testing with units in Korea and Europe.

Pace was disappointed. He said that ONTOS "had captured his imagination and the imagination of the chairmen of certain committees in Congress with which he dealt." According to the secretary, the Army staff was being "over-conservative" regarding the anti-tank system. He believed ONTOS would be an asset in the defense of Europe and emphasized its importance as a low-cost program. Furthermore, enough should be ordered to make production attractive to the manufacturer.

In response, General Collins defended the Army's approach to ONTOS and strongly reaffirmed the tank's paramount role in fighting the infantry division. The Army, he asserted, was "not opposed to change . . . it accepted new ideas and new equipment as quickly as any other organization." At the same time, since soldiers' lives and taxpayer dollars were in the balance, something new should not be produced or replace a "tried and tested" item unless it were shown to be satisfactory. But even when finally accepted, Collins argued, ONTOS could not replace the tank. US infantry divisions, he pointed out, "were organized for offensive combat, and . . . for offensive combat the tank was essential. Further, any worthwhile defense was based on the full utilization of the counterattack and for the counterattack the tank was also essential." He also cautioned against stressing ONTOS' relatively modest price tag because "economy-minded individuals would obviously find the cost differential between the ONTOS and the tank attractive."

Although still urging that ONTOS be expedited by "all practical means," Secretary Pace went along with General Collins's insistence that production not overlap service testing. Perhaps the secretary had found the chief of staff's points persuasive, or perhaps, with so little time left in office, he did not want to force a course of action so strongly opposed by the Army Field Forces, the Army staff, and Collins. In any case, Pace chose not to override the staff and interfere in the acquisition process. Nor had he done so the previous fall. The VISTA endorsement and the argument for economy were not powerful enough ammunition to use against the uniformed military's professional expertise. What Pace lacked was an analytical framework-a way to measure's ONTOS' potential effectiveness vis-a-vis the tank in countering a Soviet armored assault in Western Europe.

In the end, the Army never bought ONTOS. But the Marine Corps did and employed the system in Vietnam.

The US Marines were in the market for just such a vehicle. They were looking to replace their veteran and outdated Shermans with a replacement that was light weight, and easy to transport, they found it in the Ontos. In 1955, Allis-Chalmers put the now designated M50 into production and by 1956, was entered into Marine service with 45 of the M50s in each divisional tank battalion. Nearly 300 were built end of production in 1957.

Marines affectionately call their Ontos Hogs or Pigs. The Ontos was deployed in large numbers with the 1st and 3rd Anti-tank battalions of the 1st Marine division. By the end of 1965, a total of 65 M50s were deployed. Just as in WWII, tank crews modified their M50's to suit varying conditions.

The Marine forces involved in Operation Hue City lost 142 Marines killed in action during the month-long battle [31 January 1968 to 5 March 1968], including the initial fierce clashes involving, primarily, fighting throughout the southern sections of the city, and the climactic full-scale battles inside the Citadel fortress itself. Hundreds more Marines were wounded and had to be medevacced on both sides of the river. Enemy casualty estimates range well into the thousands.

One of the most effective aspects of supporting arms during the battle for Hue were the "killer teams" that evolved; an M-48 tank and an Ontos would pair up and maneuver together as a team. This would allow either the tank or the Ontos to maneuver into a good firing position, while the other covered. Further, the devastating firepower put out by the 90mm tank cannon and the (6) 106's of the Ontos turned out to be extremely beneficial because of their capabilities to deliver pinpoint firepower. Armored vehicles can provide many benefits to the infantry engaged in urban combat, as they provide some cover from enemy small arms fire. However, armored vehicles can also become "rocket magnets" producing casualties for infantry troops in close proximity.

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Page last modified: 07-07-2011 02:46:29 ZULU