To no one’s surprise, Israel and Hamas have resumed fighting in Gaza after almost a week of temporary truces and prisoner exchanges. Despite American and other entreaties to limit civilian casualties, Israel appears determined to push into the south of Gaza, but its strategic thinking seems to end there, and to hold no plausible endgame in sight. As a consequence, the next phase of this vicious conflict will almost certainly lead Israel to an unenviable dilemma: whether to grant Hamas a small and ultimately hollow victory or a much larger and all-too-real one. The next stages of the fighting seem clear. Israel will likely seize all of the significant aboveground urban areas in Gaza’s south, just as it did in the north. After that will come a major battle for control of Hamas’s extensive underground tunnel network, where most of the group’s fighters, leaders, equipment, and remaining hostages are presumed to be located. Ultimately, Israel may seek to destroy the tunnels themselves, perhaps by flooding them with seawater. In doing so, Israel will expect to …