A U.S.-backed Kurdish military force attempted to take back the Iraqi city of Sinjar from Islamic State militants on Thursday.

CNN reports the liberation operation, called Operation Free Sinjar, included close to 7,500 Kurdish Peshmerga fighters, who attacked the city from three sides, aided by U.S.-led coalition air strikes.

"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," said CNN correspondent Nick Paton Walsh, who accompanied one of three fronts engaged in the attack.

The operation was the largest offensive conducted by the Iraqi Kurds against ISIS so far. Walsh described the battle as more intense than the fight for the Syrian border town Kobani earlier this year. That operation was ultimately successful, but the four-month period of warfare left much of the town destroyed.

ISIS captured Sinjar last year, forcing thousands of ethnic Yazidis to flee their homes. Some headed for the nearby Sinjar mountain. Many of the men and boys who could not escape were executed by ISIS militants, while women and girls were sold into slavery.

The UN estimates close to 5,000 Yazidis were massacred.

This latest attack is not only an attempt to liberate the Yazidi community, but also to cut off the terrorist organization's supply lines between Syria and Iraq.

"One of the targets of this offensive is the highway that runs through Sinjar, known as Route No. 47 to many. Now that's very important, not only of course because of what it does to liberate the population of Sinjar -- those who've not fled ISIS rule having endured it now for over a year -- but also because it is a vital supply route towards Mosul, another key target of any future coalition offensive," Walsh said.

In a press release, the Combined Joint Task Force said around 24 airstrikes against ISIS positions in the area.