When the United States finally went to war in April of 1917 its Army was not prepared to meet the challenges that awaited it on the battlefields of Europe. What America did have, which the rest of their allies lacked, was a source of manpower that seemed inexhaustible. Under the command of General John ‘Black Jack’ Pershing, the American Expeditionary Force (AEF) raised an army of over 4 million men and was able to get half of that number sent to France by the time the war ended. The lack of suitable materiel was solved by borrowing heavy weapons and artillery from the French and British, who also trained their new allies in the ways of modern trench warfare.