New Delhi, Sept. 16 -- The U.S. withdrawal is underway, and officials say the hundreds of troops remaining in northern Iraq will be out by the Sept. 30 deadline.

The Iraqi government has linked the U.S. withdrawal to an ultimatum for militias to lay down their weapons. But most have indicated they have no plans to do so.

That leaves major questions about what the day after will look like in Iraq.

Iranian-backed Iraqi militias have struck U.S.-linked targets both inside and outside of Iraq since the U.S. and Israel attacked Iran on Feb. 28. They also have coordinated with Yemen's Houthi rebels to attack Saudi Arabia.

With the war between the U.S. and Iran raging, Tehran is unlikely to give up the leverage it has in neighboring Iraq. U....