In June 1863, Lieb was in command of the African Brigade and two companies of the 10th Illinois Cavalry during a reconnaissance mission toward Richmond, Louisiana. After encountering enemy troops, he ordered his men to withdraw. However, at the same time, Union cavalry appeared, in pursuit by Confederate cavalry. Lieb got his men into battle line and helped disperse the enemy before he retired to Milliken'³ Bend and informed his superior by courier of his actions. He remained in command, and in the battle that followed, he drove back the Confederates with the support of Union gunboats.