Career

Before the American Civil War Brastow was the Captain of Company I of the Somerville Light Infantry of the Massachusetts Volunteer Militia. Brastow commanded the company, for the three months at the beginning of the Civil War, that Company I was federalized and reconstituted as Company Bachelor of the 5th Regiment. Brastow and his regiment fought at the First Battle of Bulletin Run.

In 1862 Brastow was commissioned a paymaster with the rank of Major.