The Germans were more successful, however, when it came to devising protective measures against tank attacks. These consisted of trenches of peculiar construction and design, some of them from 15 to 20 feet wide and 6 to 8 feet in depth; “tank traps,” consisting of deep pits with camouflaged covers; bridges so built as not to support a tank’s weight; mine-fields; special tank observation-posts; _Tank Goschutz Batterie_, as the Germans called their groups of 77-mm. antitank cannon; 55-mm. tank batteries, which were kept in pits about a thousand metres from the front line and were only brought up when tanks were signalled; trench mortars mounted for horizontal fire; machine-guns firing armor-piercing bullets; hand-grenades with concentrated charges, and antitank rifles. The antitank rifle was a single-shot Mauser, mounted on a bipod, weighing 32 pounds and firing an armor-piercing ball of 13-mm. caliber. At close range this weapon penetrated the British heavy and the French light tanks. Had it been used in groups it might well have proved extremely formidable, but the unpopularity it enjoyed because of its heavy recoil combined with a well-founded reluctance on the part of its users to await the near approach of a tank, in a large measure neutralized its effectiveness. Toward the close of the struggle it seems to have fallen into general disuse, and when the Armistice was signed the enemy was preparing to supplant it with a 22-mm. machine-gun, a few of which had already been used with considerable success. * * * * * When the United States entered the war in April, 1917, the value of the tank as a weapon of offense had been so thoroughly established that steps were immediately taken to form a tank organization of our own, a special regiment—the 65th Engineers—being raised for the purpose. The units of this regiment were recruited at Camp Upton, New York; Camp Devens, Massachusetts; Camp Meade, Maryland; Camp Lee, Virginia, and Camp Cody, New Mexico, the entire regiment being assembled in March, 1918, at Camp Colt, on the battle-field of Gettysburg, which then became the general concentration and preliminary training-camp for the tank organization. The tanks passed from the control of the Corps of Engineers on March 6, 1918, when the Secretary of War directed the organization of the Tank Corps as a separate arm of the service, Lieutenant-Colonel Ira C. Welborn, a regular infantry officer, being commissioned as colonel and appointed director of the Tank Corps in the United States.