It's quite a funny story:

On the morning of July 21, 1861, civilians from Washington rode out to Centreville, Virginia, to watch a Union army made up of very green recruits—they signed up for a 90-day war—march boldly into combat. Men, women, and even children came to witness the predicted Union victory, bringing along picnic baskets and opera glasses. Bull Run soon became known as the "picnic battle." Among the civilian ranks were some of Congress's most powerful senators—many of whom had called for just such a campaign. They quickly learned that war can be unpredictable.

The Union army performed well that morning, but by early afternoon the Confederates had brought in reinforcements, forcing an intense battle over a space known as Henry Hill. When Union generals finally called retreat around 4:00 p.m., the frightened soldiers fled for their lives. "I saw the 12th New York regiment rush pell-mell out of the wood," commented one reporter. Soldiers threw down their weapons and ran from the battlefield, sweeping up civilians in the retreat.

Near the battlefield, a group of senators was eating lunch. They heard a loud noise and looked around to see the road filled with soldiers, horses, and wagons—all headed in the wrong direction. "Turn back, turn back, we're whipped," Union soldiers cried as they ran past the spectators. Startled, Michigan senator Zachariah Chandler tried to block the road to stop the retreat. Senator Ben Wade of Ohio, sensing a disastrous defeat, picked up a discarded rifle and threatened to shoot any soldier who ran. While Senator Henry Wilson distributed sandwiches, a Confederate shell destroyed his buggy, forcing him to escape on a stray mule. Iowa senator James Grimes barely avoided capture and vowed never to go near another battlefield.

Never such innocence again!