At the outbreak of the War of 1812, Biddle enlisted in the U.S. Army and was appointed a second lieutenant in the Third Artillery on July 6, 1812, and promoted to first lieutenant March 13, 1813.
Biddle enlisted in the U.S. Army during the War of 1812 and became a second lieutenant in the Third Artillery on July 6, 1812, then was promoted to first lieutenant on March 13, 1813.