Kurds launch offensive to take Sinjar from ISIS

Sinjar, Iraq (CNN)Plumes of smoke blackened the sky above Sinjar as Kurdish forces, backed by intense coalition air support, tried Thursday to take back the northern Iraqi town from ISIS.

The operation includes up to 7,500 Peshmergas -- the Kurdish military force -- who are attacking the city from three sides to take control of supply routes, according to the Kurdish Region Security Council .

CNN senior international correspondent Nick Paton Walsh is with one of the three fronts of fighters who launched their liberation operation early Thursday morning against a backdrop of airstrikes.

"A pitch-black sky was lit up by a lot of coalition airstrikes following days of bombing. At dawn, a large procession of Peshmerga started snaking their way through Sinjar mountain and behind it," Paton Walsh said.

The coalition strikes were pounding the strategic city itself, he said, with four different columns of smoke darkening the horizon above: "The strikes on Sinjar almost make the sky over it look black. There's a vast amount of air power -- more intense than the fight for Kobani."

Liberation from ISIS comes at a cost

Liberation from ISIS comes at a cost 02:19
Kobani is a Syrian border town that was wrested back from ISIS militants earlier this year after four months of fierce fighting that left parts of it entirely flattened.

Peshmerga and coalition unity
Reclaiming Sinjar is one big step toward dividing the "caliphate" that ISIS claims it is establishing across the region.