After being assigned to the 435th Fighter Training Squadron, Cashman transferred to the Vermont Air National Guard in 1999 and was a member of the 148th Fighter Squadron of the Arizona Air National Guard until 2000.

He was then assigned to the National Guard Bureau until 2008 and the Office of the United States Secretary of Defense until 2010.

After returning to the National Guard Bureau, Cashman was stationed at Joint Base Andrews from 2011 to 2012.

Cashman then became executive assistant to the chief of the National Guard Bureau.

Among his duties was serving as acting vice commander of the 128th Air Refueling Wing.