The Battle of Grand Gulf was fought on April 29, 1863, during th: Late on April 29, expecting a Union crossing of the river, Bowen sent a detachment from his command to hold Port Gibson, and the next day sent reinforcements that had arrived from Vicksburg to that place as well.[58] On the morning of April 30, the Bruinsburg crossing began.  McClernand's corps and a portion of Major General James B. McPherson's corps led the way.  By the next morning, 24,000 Union soldiers had crossed the river without opposition.[59]  More of McPherson's men crossed on May 1.[60]  Early that morning, the Confederates near Port Gibson encountered McClernand's advancing troops.[61]  The ensuing Battle of Port Gibson was a hard-fought Union victory.  Winning the battle protected the Union beachhead and rendered Grand Gulf indefensible.  Pemberton ordered Bowen to abandon the position, and the Confederates spiked the cannons there early on May 3.  Union forces occupied the position after the Confederates withdrew, and it became a supply point during the ongoing campaign.[62]  Portions of Sherman's corps crossed the river at Grand Gulf late on May 6 and into May 7.[63]