About 5.30 a.m. on the morning of July 1, the battle started. Heth probed ahead cautiously to a point about two miles west of Gettysburg. Buford's cavalry was deliberately slowing his progress. At about 10 a.m. the Union I Corps arrived commanded by General John F. Reynolds. They set themselves up along McPherson's Ridge to oppose Heth's Confederates. During the fighting Reynolds was killed but the Confederates were driven back. Meanwhile, both sides brought up reinforcements. The Union set up defenses of the town with I Corps defending the western approaches with XI Corps to the north. The flanks were covered by Buford's cavalry. One Union division was held in reserve on Cemetery Ridge. In the afternoon, when Lee arrived, the Confederates still did not know the strength of the Union forces they were facing. They also had not scouted the terrain. One division of Ewell's Corps had attacked the Union I Corps just after noon. At about 2 p.m. Heth's division joined Ewell's troops in the attack on I Corps. At about 3 p.m., another of Ewell's Confederate divisions, commanded by General Jubal Early, attacked the flank of the Union XI Corps. By 4 p.m., both of the Union corps retreated through Gettysburg and took up positions on Cemetery Ridge. So far, the Union had lost about 9,000 men including about 3,000 who had been captured. The Confederates had lost about 6,500 men by this point. So the first day of battle was technically a Confederate victory numbers-wise. But Federal troops held the high ground as more reinforcements were still arriving. Based on the first day's fighting, Lee was convinced he could defeat Meade at Gettysburg.