By late June 1863, the Confederate Army had invaded Pennsylvania, and after capturing York, the Rebels planned to take Harrisburg and possibly Philadelphia by crossing the Susquehanna River at Wrightsville. Pennsylvania militiamen from Columbia on the Lancaster County side of the river, joined by Union troops and a company of African American militiamen, gathered fewer than 1,500 men to block the advance. When Confederate Brigadier General John Brown Gordon arrived on June 28 with approximately 1,800 troops, the Federals waited in entrenchments, but Confederate artillery fire quickly made their position untenable. The Federals retreated to Columbia and tried to destroy a section of the more than mile-long bridge behind them to deny the Confederates access to Lancaster, but when explosions failed to bring it down, they ordered it burned. As Confederate forces surged forward, the bridge burst into flames, and although Gordon's men worked for hours to stop the fire and prevented Wrightsville from being consumed, the bridge was destroyed. Gordon's brigade was recalled to York the next day, and the Pennsylvania militia had saved Lancaster.