The U.S. military announced on Wednesday that it has completed the withdrawal of all American troops from Iraq, ending a 12-year mission to fight the Islamic State group. The last U.S. troops left an air base in northern Iraq under a deal between Baghdad and Washington.

The withdrawal, agreed on two years ago, comes against the backdrop of the ongoing war between the United States and Iran that has also sometimes spilled over into Iraq, with Iran-backed militias firing on U.S. troops and the U.S. striking the groups’ strongholds.

In recent years, Washington has appeared to seek to shift its focus from the Middle East toward Asia, but that shift has been inconsistent, with the Pentagon alternating between reducing its Mideast presence and then finding itself engaging in new conflicts — including the ongoing war in Iran.