The fighting opened on the morning of May 12 when the leading Union troops ran into skirmishers sent out by Granbury. The Union troops were surprised to meet resistance, and skirmishing began at a range of about . Bledsoe's cannons also began firing at the advancing Union troops. At around 09:00, McPherson realized that the Confederates in front of his force represented more than just skirmishers, and began deploying for battle. McPherson used cavalry to cover his flanks and brought Brigadier General Elias Dennis's brigade, which consisted of four regiments, three of which were from Ohio, to the front. Dennis's brigade was halted by Confederate infantry and artillery fire, and the Confederates attacked, hitting the 20th Ohio Infantry Regiment hard. Surprised, the Union line began to buckle, but was rallied by division commander Major General John A. Logan. McPherson, in his inexperience, overestimated the strength of the Confederate force he was facing.