美国920毫米迫击炮

kirov

As winter turned into spring in early 1944, plans were rapidly nearing completion for the invasion of Nazi Europe. Every contingency had been provided for; every item of essential supply was on its way. Intelligence reports leading out of the tortured continent indicated that the German High Command was hastily preparing several powerful switch lines of defense.

kirov

Defensive works based on experience gained in construction of the Siegfried Line were planned for the great river barriers of the Loire, Seine, and Marne, with offshoots to seal the bases of the great peninsulas jutting out into the Atlantic. These works consisted of partially buried, reënforced-concrete redoubts studded along the defensive lines at a frequency of twenty-five to the mile in the important sectors. Each echelon in the defense chain was to be some 50 feet long, 30 feet wide, and 17 feet high, with roofs and walls of reënforced-steel 7 feet thick.

kirov

Military prudence demands adequate plans to meet any eventuality. Should out invasion forces surging over the beachheads be halted, means must be provided to overcome the defense and maintain the tempo of the attack. Experience indicated that existing field-artillery weapons could not accomplish the task without excessive losses and at practically point-blank ranges. Thus a new solution was urgently required.

kirov

Early in March the Army Ground Forces expressed their grave concern and presented the problem to the Research and Development Service of the Ordnance Department. At a conference in Maj. Gen. G. M. Barnes’ office on the eleventh day of March, the “Little David” project was initiated. Translating the problem in turn from the nature of the target to the projectile requited to encompass its destruction and thence to the weapon, General Barnes logically bounded and defined the engineering problem.</P>

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It was calculated that the destruction of these German fortifications would require a weapon that could hurl a monstrous projectile weighing more than 3,200 pounds a distance of at least 7,500 yards. Firing from a protected position in defilade it would require such refined accuracy that a totally destructive hit would be registered on each redoubt in but one or two shots.

kirov

The weapon had to be readily transportable over existing highways, highly mobile and independent of rail movement. It had to be capable of being emplaced after darkness, fired by midnight, and withdrawn before daylight after its deadly mission had been accomplished. Initial deliveries were specified for six months from date of initiation of the project.</P>

kirov

To meet these specifications it was determined that a gigantic mortar of 36-inch bore would be required. The ammunition would bear a striking similarity to two bathtubs welded rim to rim. To ensure road mobility, two enormous tank transporters would be needed, one for the 38-foot rifled tube and the other for the base mount and recoil system.

kirov

It was obvious that to meet the specified delivery dates maximum use would have to be made of standardized components, but they were nonexistent except commercial motors, pumps, valves, electrical controls, and the sighting telescopes with their quadrants. All other parts required to handle this equipment, such as hydraulic jacks, supporting equipment, and dollies for transportation, had to be produced.</P>

kirov

As a background of experience, Ordnance had been developing 6- and 10-inch mortars which in no sense presented comparable problems. Sketchy information was available on the German supercannons which represented the most colossal efforts of Krupp domain (see <I>Army Ordnance</I> November-December 1946, p. 254). Even the data was of little value since the Nazi weapon was five inches smaller in caliber, required a train of twenty-five cars to move, and emplaced on parallel rail tracks, three weeks being needed to complete the installation.</P>

kirov

Acting upon the advice and with the counsel of that eminent friend of Ordnance, Frank B. Bell, the gravity and difficulties of the problem were presented to Lorenz Iversen, president of the Mesta Machine Company. No wiser choice could have been made. Working in complete disregard of personal stain and as much as 16 to 18 hours a day, he had blocked out the basic design of the world’s largest cannon by the time a contract was received on May 9, 1944.</P>