In the pre-dawn hours of 8 October 1862, Army of the Ohio commander, Major General Don Carlos Buell ordered Gilbert to seize Peters Hill. Gilbert passed the order to Sheridan who assigned McCook's brigade to capture the hill. Sheridan had two veteran brigades, but he used McCook's regiments even though they were untried in battle, possibly because he assumed that the hill was unoccupied. Just before dawn, McCook's brigade chased the 7th Arkansas Infantry Regiment off the hill after losing 6 men killed and 27 wounded. At daybreak, there was an artillery duel during which the 125th Illinois supported Barnett's Battery I, 2nd Illinois Artillery and suffered some casualties from shrapnel. The 7th and 5th Arkansas Infantry Regiments counterattacked but were repulsed by McCook's brigade, including rifle fire from the right wing of the 125th Illinois. Late in the afternoon, Sheridan's division was attacked by Colonel Samuel Powell's brigade. Sheridan's division was deployed somewhat haphazardly, with the 125th Illinois far to the rear. Nevertheless, Powell's outnumbered Confederates were beaten and driven away. The 125th Illinois sustained losses of 1 killed and 8 wounded at Perryville.