General John J. Pershing, Commander-in-Chief, American Expeditionary Forces, appointed Colonel Samuel D. Rockenbach, Chief of the Tank Corps on December 23, 1917. The Americans were assembling their forces to deploy to the European theatre of war and did not have tanks in their inventory. The war, with its barbed wire, trenches, gas and machine guns needed an armored big gun to shoot through all those defenses. Rockenbach would have to decide on the type of tank, organization, training, tactics and logistics–and he had only nine months before the first American tank units entered combat at the Battle of St. Mihiel. He details his amazing story in Operations of the Tank Corps A.E.F.