As many have observed, these flashpoints show the growing reach of the so-called axis of resistance, the loose group of Iranian-backed militias that is attacking Israeli and U.S. interests across the Middle East. Less noted, however, has been the extent to which this broader conflict has blurred the sectarian divisions that have often shaped the region. After all, the vicious civil wars in Iraq, Syria, and Yemen have all had a Sunni-Shiite component; for years, Iran and Saudi Arabia have invoked sectarian loyalties in their long-running contest for regional dominance. Yet the war in Gaza has defied this tension: Palestinians are overwhelmingly Sunni Muslims, and Hamas emerged out of the Muslim Brotherhood, the most important Sunni Islamist movement, with roots in Egypt. How is it that Hamas has found some of its strongest allies in Shiite-led groups and regimes in Iran, Iraq, Lebanon, Syria, and Yemen?