Report: U.S.-backed forces launch operation against ISIS in northern Syria

Syrian forces backed by the United States launched an offensive on Tuesday to capture what one U.S. official called the Islamic State's "last remaining funnel" to Europe, Reuters reports.

The area of northern Syria known as the Manbij pocket has been used by ISIS to move foreign fighters back and forth to Europe, and a goal of the operation is to isolate ISIS and cut off the supply line to its de facto capital, Raqqa. Thousands of fighters have been preparing for the offensive for weeks, U.S. officials told Reuters, and while some U.S. special operations forces will serve as advisers and offer support on the ground, they will not engage in direct combat. The operation will also involve airstrikes from the U.S.-led coalition and firing positions from the ground in Turkey.

The forces are mostly composed of Syrian Arabs, with about one-sixth of them members of the Kurdish YPG militia, officials said. Turkey views Syrian Kurdish YPG fighters as terrorists, and opposed the idea of the militia taking control of the Manbij pocket, Reuters reports.