During early summer of 1861 Confederate forces were organizing around Centreville and Manassas while the Union army was encamped along the Virginia side of the Potomac River. Both sides sent forces into Fairfax County to scout and forage.
About 6pm on June 17, 1861, four companies (271 men) of the 1st Ohio Infantry under the command of General Robert Schenck were scouting west from Falls Church aboard a train on the Loudoun and Hampshire Railroad. As they approached the Vienna Station Confederate infantry and artillery under the command of Colonel Maxey Gregg of the 1st South Carolina Regiment opened fire on the train with two cannon and their rifles.
Several cars were destroyed in the engagement, and the Union soldiers jumped from the railroad cars and sought cover in the nearby woods. The engineer unhitched the cars, left the troops behind, and raced the locomotive back to Alexandria. Eight Union troops were killed in the skirmish but the rest of the Federal troops were able to withdraw on foot back along the line towards Falls Church. This would go down in history as the first time a train was engaged in warfare in US history.