Official: 'We're like the Marines of the church': "Seven young adults gather for informal Sunday worship in a rude, two-room house fashioned from plastic sheeting and lumber that they cut themselves. Clad in shorts and jeans and clutching well-thumbed Bibles, they join in song to guitar accompaniment."

"The melody drifts across a surrounding makeshift encampment where 28 students have spent the last two weeks, the final exercise in a unique training program for the most exotic vocation imaginable.

"This is the Missions Institute of New Tribes Mission, a yearlong boot camp that's far more rigorous than the usual orientation programs for foreign missionaries—and for good reason."