NATO will expand its security training mission in Iraq by thousands of troops following a deadly rocket attack on a military airbase earlier this week.

The 30-member alliance will increase its personnel in Iraq from 500 to around 4,000, a move to prevent the war-torn country from becoming a breeding ground for terrorists, NATO Secretary-General Jens Stoltenberg announced Thursday.

“ISIS still operates in Iraq and we need to make sure they’re not able to return,” Stoltenberg told reporters at the end of a two-day virtual NATO defense ministers meeting.

What the increase means: He said NATO’s efforts will now include more Iraqi security institutions and areas beyond Baghdad, though their presence “is conditions-based and increases in troop numbers will be incremental.”

He added that the Iraqi government had made a request for the expanded mission, which will begin in the coming months.

The forces already there: NATO has been in Iraq since 2004 to train Iraqi security forces. Its current training mission, which began in 2018, is meant to help the Iraqi forces prevent ISIS from resurging. 

The increase in NATO troops could possibly ease pressure on U.S. forces in Iraq, where about 2,500 troops are based for a mission separate from the alliance.

Will the US also increase?: A senior Defense official told reporters earlier this week that the Pentagon “welcomes NATO’s increased focus on Iraq,” but would not say if the U.S. would add more troops to the training mission.

Response to attack: Plans for an expanded NATO footprint follows the rocket attack Monday on Erbil International Airport, a military airbase in northern Iraq, which killed a civilian contractor and injured nine people, including a U.S. service member.

The militant Shia group Saraya Awliya al-Dam claimed credit for the attack, though the Biden administration has not publicly confirmed who is responsible for the strike.

The State Department on Wednesday vowed “consequences for any group responsible for this attack.”