May 1 marked a turning point in the battle. The Union forces had a very good plan which they executed extremely well in early stages. However, the Union troops stopped at Chancellorsville in the early afternoon of April 30 and did not move out for almost 24 hours. This gave time to the Confederates to react. Finally on the late morning of May 1, Sykes' Division marches out on the Orange Turnpike as depicted in this sketch. Confederates under "Stonewall" Jackson aggressively advanced toward them.
The forces clashed here on what is now known as the May 1 Chancellorsville Battlefield. This photo is facing east, the direction the Union forces were advancing. The initial Confederate position was on a very slight rise shown here near the farm house in the right center of the photo.
Despite having all the advantages, General Hooker made a crucial decision to withdraw to Chancellorsville. By doing so, he gave up open ground that his troops needed in exchange for fighting in the dense woods of the Wilderness. More importantly, he surrendered control of the initiative to Lee and Jackson.