Backed by a barrage of U.S.-led airstrikes, Kurdish forces on Thursday encircled Islamic State militants in Sinjar, a town that sits astride a key supply route to Syria and whose fall could presage a later assault on the extremist group's major Iraqi stronghold, Mosul.<br />The three-pronged attack on Sinjar involved some 7,500 Kurdish peshmerga fighters, including thousands of minority Yazidis battling to retake their homes.<br />The Islamic State's capture of the town last year precipitated an American air campaign after thousands of Yazidis became stranded on nearby Mount Sinjar.<br />The largest offensive yet launched by Iraqi Kurds against Islamic State forces, the battle is a key test of their military capabilities.
