Professor Hollenbaugh served as an EA-6B naval flight officer with tours based in the U.S. and Japan with Naval Forces Japan. Ashore, he served as an instructor at the EA-6B fleet replacement squadron and as an international engagement desk officer at OPNAV N52. In addition, following joint military attache school, Hollenbaugh served two tours overseas as the defense attache to the Republic of Albania and the naval attache to the Republic of Bulgaria.