The conflict in Syria has captured the imagination of Indonesian extremists in a way no foreign war has before. For the first time, Indonesians are going overseas to fight, not just to train, as in Afghanistan in the late 1980s and 1990s, or to give moral and financial support, as in the case of Palestine. The numbers are still limited – the Indonesian foreign ministry estimated about 50 in December 2013 – but they could rise.

Four factors explain why the conflict has attracted such attention. First, the enthusiasm for Syria is directly linked to predictions in Islamic eschatology that...