Before the battle, the Seven Day's Battles happened which forced union soldiers back to Richmond. Lincoln would not have any of this. He ordered General John Pope to fight back.
Stonewall Jackson wanted to defeat Pope's army before the two union forces murged together. Jacksons troops met pope's army at bull run and started another fight.
The first day of fighting was savage, and both sides had many deaths, which came to a standstill among them. The second day pope tried to do a sneak attack but again, both sides had many deaths.