Fighters of the Islamic State militia took control Sunday of the largest dam in Iraq, a reservoir of oil and three cities after breaking the biggest defeat the Kurdish forces since they began operations in the region in June. Capturing the Mosul dam after just 24 hours' offense could give the Sunni militiamen ability to flood the big cities, as part of its campaign to topple the Shiite government of Prime Minister Nuri al-Maliki. The Islamic State, which considers the Shiite majority in Iraq as apostates who deserve death, also captured the site of Ain Zalah, adding four others who are already under their control, and three cities. The insurgents met with strong Kurdish resistance only at the beginning of his latest offensive, when they took the city of Zumar.