US faces another major Middle East troop withdrawal, but threat remains

The U.S. military is scheduled to end its mission in Iraq on Wednesday, bringing to a close a military operation that has lasted more than two decades — despite an ongoing war in Iran sparked earlier this year.

The Iraq mission began with the 2003 invasion that toppled Saddam Hussein and later evolved into a campaign to help Iraqi forces defeat the Islamic State group after the terrorist organization’s rapid rise across Iraq and Syria.

In recent years, however, the remaining U.S. military presence has increasingly served as both a counterweight to Iran’s influence and a frequent target of Iran-backed militias...