Although Beauregard had little concentrated strength available to oppose a southward movement by Halleck, the Union general showed insufficient drive to take advantage of the situation. He waited until he assembled a large army, combining the forces of Buell's Army of the Ohio, Grant's Army of West Tennessee, and Pope's Army of the Mississippi, to converge at Pittsburg Landing. He moved slowly in the direction of the critical rail junction at Corinth, taking four weeks to cover the from Shiloh, stopping nightly to entrench. By May 3, Halleck was within ten miles of the city but took another three weeks to advance eight miles closer to Corinth, by which time Halleck was ready to start a massive bombardment of the Confederate defenses. At this time, Beauregard decided not to make a costly defensive stand and withdrew without hostilities during the night of May 29.