As part of the U.S.-backed effort to capture Mosul, ISIS surrendered Baaj in northwest Iraq this weekend, which U.S. and Iraqi sources believe was a hideout for ISIS leader Abu Bakr al-Baghdadi, per Reuters.

Why it matters: This is another indication that ISIS's control of northern Iraq is dissipating (after losing Falluja, Tikrit, Ramadi, and most of Mosul). ISIS held Baaj since mid-2014 and Islamic militants controlled it for 14 years.

What it means: The fight against ISIS is going to shift to Syria; ISIS remains in only a couple urban centers in Iraq now, a spokesperson for the DOD confirmed to Axios.

Complicating factor: Iran is aiding in the campaign to gain land in northern Iraq to establish a military supply route for Syrian President Bashar al-Assad. Last month, Defense Secretary Jim Mattis said the U.S. "will never work with the Assad regime."