While an estimated 1,000 foreign fighters continue to flow into Syria each month, with a small-but-growing number of Americans, very little is publicly documented about the recruitment pipeline — a well-oiled machine that has attracted fighters from all over the world.

Once in Syria, John says he met a Canadian, other Americans and Britons. It is a confusing legal situation. The U.S. military backs Kurdish operations while the State Department discourages direct involvement by U.S. citizens.