Troop Levels
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Prior to entry into World War I, the United States had a small standing army. Between 1914 and 1916, the total number of United States service members remained relatively stable at around 175,000 members. However, after the Congress declared war on April 6, 1917, the United States quickly mobilized a large military force.
In 1918, the United States had 2,897,167 service members in all branches of the military. Of those, 2,395,742 served in the Army, 448,606 in the Navy, and 52,819 in the Marines Corps.
