Final answer:
During the parley to start the battle, both armies unintentionally ran into each other while maneuvering. This chance encounter escalated into a full-blown battle, resulting in the Confederates emerging victorious and the Union forces falling back.
Step-by-step explanation:
During the parley to start the battle, both armies unintentionally stumbled upon each other while maneuvering to their intended positions. Realizing they had encountered the enemy, each side formed and prepared for combat. The chance encounter quickly escalated into a full-blown battle with 30,000 Confederates facing 20,000 Union soldiers. The Confederates emerged victorious, driving the Union forces back, and both sides subsequently formed defensive positions as more units arrived in the area.