The size and duration of the siege in Marawi City make it difficult to determine the jihadists' intentions for the attack. The Philippine government and armed forces have labeled it a hostage scenario, but the militants occupying the area seem to have a more ambitious goal in mind. Fighters from the Maute group and Abu Sayyaf brandished Islamic State flags and occupied government buildings early on in the attack in a scene reminiscent of the siege of Mosul in 2014. A week into the siege, moreover, the militants released a video in which one of the captives, a Catholic priest, referred to the civilians under their control as "prisoners of war." But while the incident is unprecedented as a hostage scenario, it is far less spectacular as a bid to claim territory. The attempt falls far short of the Islamic State's land grabs in Syria and Iraq, and it hasn't...