On April 30, 1863, Maj. Gen. Ulysses S. Grant's army crossed the Mississippi River at Bruinsburg, 30 miles south of his objective of Vicksburg. Grant hoped to move east toward the capital at Jackson to block the Confederate army there under Gen. Joseph E. Johnston from reinforcing Vicksburg. Port Gibson, ten miles east of Bruinsburg on the Bayou Pierre River, commanded the best approach routes and was the first Federal objective. A Confederate force there was commanded by Maj. Gen. John S. Bowen. Grant's Army of the Tennessee was composed of the Seventeenth Corps under Maj. Gen. James B. McPherson, and the Thirteenth Corps under Maj. Gen. John A. McClernand. Fierce night fighting erupted early on May 1st as the Union soldiers encountered Bowen's men in the craggy, overgrown tangle around Port Gibson shortly after midnight. After a brief lull, the battle roared to life once more at dawn. Confederate Gen. Edward Tracy was killed while directing the defense of the right flank from McPherson's attacks. The battle continued for most of the day as successive Confederate lines buckled under the weight of the Union advance. A counterattack was repulsed in the late afternoon and the Southerners were forced from the field. The Battle of Port Gibson firmly secured a Union beachhead east of the Mississippi River and enabled Grant to push east unopposed toward Jackson.