So for the sake of their children, al-Mousa says, he and his wife made a pact: He’d leave them behind in Aleppo and make the perilous journey to Holland, and when he got legal status, he’d bring them along.

Al-Mousa is hardly alone. Many of the men I interviewed traveling solo told me they had left their families behind and intended to reunite with them once they’d been accepted by a safe European country.

This helps to clarify why so many of Europe’s newcomers are young men. Of 102,753 registered arrivals through Italy and Greece, the International Organization of Migration found that 68,085 were men, with only 13,888 women and 20,780 children. At both the Hungary-Croatia border and the Serbia-Croatia border, I saw a noticeable majority of men, though it was nearly impossible to take a photograph without capturing at least one woman or child in the background.

“They tell us, ‘We do this dangerous trip on our own, we get asylum, and there is a law in the European Union that the family can come,’” says Christof Zellenberg, the chairman of the Europa Institute, who has been heavily involved in volunteer efforts in Vienna. You see few newcomers over 50, he adds, because “this is a grueling trip, and you need to be young and strong.”