Capt. Rye Barcott has spent months under stress, like most other U.S. Marines in the Iraq War zone.
"It's enormously draining when you're outside the wire and under danger … where the enemy really is faceless," he said.
But there's been double stress for Barcott. Unlike most American troops in Iraq, the 27-year-old has been fighting two battles in different countries.
His other war is a personal campaign he runs by phone when in Iraq, is 2,400 miles away from the Middle East -- in Africa.
In between combat assignments in Iraq, Barcott's private mission in Kibera, a slum in Nairobi, Kenya, is to prevent rival African tribes from erupting into sectarian warfare.
"I'm hoping that Kibera doesn't become a situation like Iraq, [that] it doesn't degenerate into ethnic violence," he said.
Barcott first came to Kibera as a student at the University of North Carolina and was shocked by what the outside world had largely ignored -- 700,000 people on a patch of land the size of New York's Central Park, living in desperate conditions.
"It's not right for folks to live like this," he said. "We've gotta do something about poverty."
Tensions between rival tribes had already erupted into riots. Barcott started his own personal foreign policy, in the hope that one American could make a difference in such an ethnic powder keg.
He gave up the comforts of his home in North Carolina, moved to Kibera and formed a charity, Carolina for Kibera, that turned the slum's shacks into a medical clinic and a youth center.
Now Barcott even has rival gangs cleaning the streets together and playing soccer. If they want to win, he said -- and most kids do -- then they have to trust teammates who could be their enemy off the field.
When he joined the Marines, Barcott took his war on African poverty with him, raising donations of $10,000 a year -- about what the U.S. government spends in Iraq every three seconds. When in Iraq, he keeps in touch with his African charity almost every day.
He has advice for other young Americans.
"If you have the means to travel, get out of your comfort zone," he said. "Expose yourself to how the majority of the world lives … and I think it'll make you a lot more appreciative of what you've got … make you a better American and a better global citizen."