Adna Romanza Chaffee was a lieutenant general in the United States Army. Chaffee took part in the American Civil War and Indian Wars, played a key role in the Spanish–American War, and fought in the Boxer Rebellion in China. He was the Chief of Staff of the United States Army from 1904 to 1906, overseeing far-reaching transformation of organization and doctrine in the army.

The chief of staff of the Army (CSA) is a statutory position in the United States Army held by a general officer. As the highest-ranking officer assigned to serve in the Department of the Army, the chief is the principal military advisor and a deputy to the secretary of the Army. In a separate capacity, the CSA is a member of the Joint Chiefs of Staff and, thereby, a military advisor to the National Security Council, the secretary of defense, and the president of the United States. The CSA is typically the highest-ranking officer on active duty in the U.S. Army unless the chairman or the vice chairman of the Joint Chiefs of Staff are Army officers.