[2] After graduating, Robbins enlisted into the United States Army to serve in the Spanish-American War.

After the war, Robbins enrolled at Columbia Law School and enlisted in the New York National Guard.

In 1909, Governor Beryl F. Carroll appointed Robbins as a judge on the superior court of to the Cedar Rapids, Iowa.

During World War I, he served as adjutant to Brigadier General Hubert Allison Allen at Camp Cody, New Mexico.

[2] In January 1928, President Calvin Coolidge appointed Robbins as Assistant Secretary of War, succeeding Hanford MacNider.