With his regiment Cameron participated in the 1863 Vicksburg Campaign, where he was slightly wounded in his eyes during the Battle of Port Gibson on May 1. Cameron was promoted to brigadier general in the Union Army on August 11, 1863. After several stints of brigade command in late 1863 and 1864, he led a division of the XIII Corps during the 1864 Red River Campaign. During the Battle of Mansfield in Louisiana on April 8, Cameron's men attempted to reinforce the crumbling Union line around 5 p.m., but were forced back when it finally broke near 6 p.m.