Members of the Brandywine Home Guards (two militia companies comprised of workers from DuPont and other Brandywine businesses) elected Stirling to command Company B shortly after the unit's formation in April 1861. Captain Stirling, despite a lack of military experience, was responsible for teaching his men the basics of being a soldier. Members of these companies received drill and instruction on nights and weekends so they could keep their jobs.
By the summer of 1861 the Brandywine Home Guards assumed the duties of protecting business along the Brandywine.
Federal and state military officials decided to create a regiment from several Delaware militia companies in October 1862. This new unit was designated the 5th Regiment Delaware Volunteer Infantry. Hugh Stirling's company of the Brandywine Home Guards became Company D of the 5th Delaware. Stirling remained commander of the company with the rank of Captain. Stirling went with his company to Fort Delaware when the regiment was called into active service on 20 June 1863. There he guarded Confederate prisoners until his company was reassigned to protect the DuPont powder works on 14 July. Hugh Stirling was mustered out of service on 12 August along with the rest of the 5th Delaware.
Image: Letter from Hugh Stirling to Lammot du Pont, 1862 (Hagley Digital Archives)