ISIS retakes strategic Syrian city

Backed by U.S.-led coalition airstrikes, Kurdish forces wrested control of Ain Issa and Tal Abyad last month.

Both cities are strategically important, because they sit along a supply route on a main road between Raqqa, the city ISIS considers to be its capital, and the Turkish border.

The development comes after a weekend of coalition airstrikes on ISIS targets in Raqqa, described by Brett McGurk, the U.S. envoy for the coalition against ISIS, as "the most sustained set of airstrikes to date" against ISIS in Syria.

(CNN)