McClatchy reports: A Syrian Kurdish offensive described last week by U.S. officials as the most effective assault to date on the Islamic State has ground to a virtual halt because of Turkey’s opposition to the advance and Kurdish commanders’ reluctance to extend their frontlines beyond Kurdish areas, Syrian Kurdish and Arab militants say.

The stalling of the offensive, which was aided by U.S. airstrikes that were coordinated with Syrian Kurdish fighters on the ground, deals a new setback to the Obama administration’s efforts to build an anti-Islamic State coalition among Syrian opposition forces, and it comes amidst a buildup of Russian jet fighters, armored vehicles and personnel near Syria’s coast.

“The Kurdish forces are important because they are America’s boots on the ground in Syria and Iraq,” said Soner Cagaptay, an expert with the Washington Institute for Near East Policy, a think tank.

The slackening in the drive by the Peoples Protection Units, a Syrian Kurdish militia known as the YPG, can be traced through the dramatic drop in the rate of U.S. airstrikes launched against the Islamic State in areas inside and adjacent to the swath of territory along the border with Turkey from which the brutal Islamist movement was expelled by the YPG offensive. [Continue reading…]