In my fifteen years as a member of the US Army, I was one of the few I knew who had no belief in God. I wasn't vocal or outspoken about it, but when questioned about my views or asked to go to "services" on Sundays, I was always honest about it.
Some people in far more difficult circumstances than I was put in have had their "lack of faith" tested even more strenuously. Benjamin Tupper is one of them. His story is both enlightening and heart-rending. That he was able to maintain a strong role in such a difficult situation, leading both Christians and Muslims in battlefield conditions, is inspiring. Even though those serving with and beneath him continually told him he was 'going to hell', he didn't relent and he lead them with honor. He even won the respect of the Afghani interpreter who was assigned to his unit (although the boy remained a Muslim).
Not everyone who serves is religious -- and those without religion are just as dedicated, caring and inspiring -- perhaps more so because they do it without promise of a heavenly reward (and often in the face of those who would have them 'hellbound').