Kurdish Iraqi fighters, with the help of at least 20 U.S.-led airstrikes, launched an offensive early Thursday to reclaim the ISIS-held town of Sinjar. More than 7,500 Peshmerga fighters began an assault on the mountain town as part of an effort to retake it and cut off a strategic supply route for ISIS militants between Syria and Iraq’s Mosul, according to a statement from the Kurdish Regional Security Council. A U.S. official close to the operation told The Daily Beast that hundreds of ISIS fighters had well-prepared defenses within Sinjar, and a fierce fight was expected. The aim of the push was also to establish “a significant buffer zone to protect the city and its inhabitants from incoming artillery.” ISIS seized control of Sinjar in August 2014, sending thousands of the minority Yazidi community to flee. Many were killed in the assault while hundreds were kidnapped and enslaved.