Grant's men drove inland, and defeated a Confederate blocking force at the Battle of Port Gibson on May 1; the batteries at Grand Gulf were abandoned the next day. Grant was then forced to make another choice: he could move north towards Vicksburg, or head east and later turn to the west and attack Vicksburg from that direction. Both lines of advance had the potential to capture the city, but the latter option provided a better chance of also capturing the Confederate garrison and its commander, Lieutenant General John C. Pemberton. Grant put his plan in motion by having Sherman's XV Corps cross the Mississippi River at the now-abandoned Grand Gulf position and then drive towards Auburn. To Sherman's left, Major General John A. McClernand's XIII Corps covered the crossing of the Big Black River, and on the Union right was Major General John B. McPherson's XVII Corps. McPherson, who was lacking experience leading a sizable body of men in independent command, was directed to advance to Raymond via Utica. McPherson's advance was resisted by little other than militia. Union cavalrymen raided the New Orleans, Jackson and Great Northern Railroad, and the advance frightened local residents. On May 11, Grant ordered McPherson to take his command to Raymond and resupply there, while maintaining the impression that he was targeting Jackson.