He was an important recruiter of black men into the United States Colored Troops.

He campaigned for Abraham Lincoln in 1860 and was a leader in the Wide Awakes and at the outbreak of the Civil War joined a militia company led by abolitionist Cassius M. Clay which organized to guard the president and the White House.

[1][2] Mussey supported the anti-slavery movement and was in favor of the enlisting of black troops in the war.

[4] As a captain of the 19th U.S. Infantry Regiment from May 14, 1861, until June 14, 1864,[2] Mussey helped recruit African-American soldiers for the Union Army, being detailed to act as a commissioner for organizing black troops with headquarters at Nashville.

[2][6] Mussey was mustered out of the volunteers on December 26, 1865, and resigned from the regular army on February 19, 1866.

[2] Religiously, he was a member of The New Church[1] On Page 270 of Medical Record, Volume 1, edited by George Frederick Shrady, Thomas Lathrop Stedman.