After returning from a deployment to Iraq in 2007, Cartwright volunteered to become a canine handler. He partnered with Isaac, a black Labrador retriever, at the Military Working Dog Program or “Dog School,” at Lackland Air Force Base in San Antonio. The two became a close-knit team after completing the nearly 6-month training program. Since then, Cartwright and Isaac have served two tours of duty in Afghanistan locating explosive devices planted by terrorists near roads, hospitals, schools and military facilities.