Bronson was born enslaved in 1838 in Indiana County, Pennsylvania.
After gaining his freedom, he enlisted in the Union Army in 1863 as a private in Company D of the 5th Colored Infantry Regiment. By September 29, 1864, he had risen to the rank of first sergeant. On that date, he was among a division of black troops assigned to attack the Confederates at New Market Heights.
The attack was met with intense fire and many of the regiment’s officers were killed or wounded in the charge, including the regimental commander and all of Company D’s officers. Bronson took command of Company D and led a renewed attack which successfully captured the Confederate positions. For his actions, Bronson was awarded the Medal of Honor, America’s highest military decoration, on April 6, 1865.