Kurdish peshmerga forces, backed by smaller militias, are trying to recapture the ISIS-held city of Sinjar in northwestern Iraq.
The offensive is receiving support from the U.S.-led anti-ISIS coalition. Dozens of airstrikes have targeted ISIS positions in and around the city leading up to Thursday's offensive and are continuing.
The goal is to not only liberate Sinjar, but also to cut off a key ISIS supply route stretching from Raqqa, in Syria, to Mosul, in Iraq.
ISIS overtook Sinjar last year in August.
The siege created a humanitarian crisis. Thousands of Yazidi minorities fled to Mount Sinjar — the very mountain peshmerga are now using as staging ground to retake its namesake city.
Although recapturing Sinjar wouldn't entirely cut off ISIS' supply lines between Syria and Iraq, it would hinder it quite a bit.
The Kurdish peshmerga will still face a tough fight within Sinjar. A Buzzfeed reporter who spoke with fighters on the ground was told IED traps are hidden in as many as 70 percent of the neighborhoods.