When the Spanish-American War began, the U.S. Army was at its lowest level of strength since the Civil War (1861–1865). The number of officers and enlisted men was 28,000. There were not enough troops to fight a war.
To increase the number of soldiers, President William McKinley called for state volunteers. More than 125,000 men joined National Guard and militia units. Some units were sent to the Philippines. Other units were formed into the Fifth Army Corps commanded by Major General William R. Shafter. Shafter was ordered to lead an invasion of Cuba.
