Floyd was a surgeon with the rank of major in the Virginia State Militia from 1807 to 1812. At the outbreak of the War of 1812, Floyd moved his family to a new home near present-day Virginia Tech to be near friends and entered the regular army. On July 13, 1813, he was appointed surgeon of Lt. Col. James McDowell's Flying Camp in the Virginia militia. When he returned from a leave of absence, he discovered someone else had been appointed to replace him, and so his service in this role ended on November 16, 1813. Floyd was then commissioned as major of the militia on April 20, 1814 and was promoted to the rank of brigadier general of the 17th Brigade of Virginia militia. He served until he was elected to the Virginia House of Delegates in 1814. During this time, he moved his family again, this time to Thorn Spring, a large plantation in Montgomery County, Virginia. Thornspring (Pulaski) (now Thornspring Golf Course) was inherited by Letitia Preston Floyd from her father William Preston and was located near her older brother, Virginia Treasurer, Gen John Preston, and his Horseshoe Bottoms Plantation (now the site of the Radford Army Ammunition Plant). They both were near the Preston's home at Smithfield plantation (now the campus of Virginia Tech) that their father had completed in Montgomery county for their mother, Susannah Smith Preston, before he died. John Floyd used to keep Bears chained to the tree on the lawns of the Thornspring Plantation (Pulaski, Virginia).