Fort Willard is a former Union Army installation now located in the Belle Haven area of Fairfax County in the U.S. state of Virginia.

The U.S. Army responded by creating the Department of Washington, which united all Union troops in the District of Columbia and Maryland under one command.

In the days that followed the Union defeat at Bull Run, panicked efforts were made to defend Washington from what was perceived as an imminent Confederate attack.

[5] The makeshift trenches and earthworks that resulted were largely confined to Arlington and the direct approaches to Washington.

On July 26, 1861, five days after the battle, Maj. Gen. George B. McClellan was named commander of the military district of Washington and the subsequently renamed Army of the Potomac.

There was nothing to prevent the enemy shelling the city from heights within easy range, which could be occupied by a hostile column almost without resistance.

[9] Lieutenant Colonel William S. Lincoln of the 34th Massachusetts explains in his memoirs that on January 8, 1863 General Barnard, along with a "party of engineers," spent the day running lines for an additional Fort, to be connected by covered ways and rifle pits, with the redoubts we have been constructing; and Lieutenant Schenck [engineer in charge] communicates the not very agreeable information, that the 34th will be required to build the new works.

[10]The fort was named in honor of Colonel George L. Willard, who was killed at the Battle of Gettysburg, on July 2, 1863.