U.S. personnel suffered brain injuries in a ballistic missile attack Saturday.
The U.S. on Tuesday staged airstrikes against Iran-backed militias in Iraq in retaliation for ballistic missiles fired Sunday against Al-Assad airbase that left four U.S. personnel with traumatic brain injuries, two U.S. officials said.
Sunday's attack on U.S. troops at the sprawling Iraqi airbase in western Iraq involved 17 ballistic missiles and rockets and was launched from inside Iraq, according to three U.S. officials.
While the majority of the projectiles were blocked, two ballistic missiles were able to get through U.S. air defenses, the officials said.
The Pentagon said that the attack resulted in structural damage to "noncritical facilities" and that four U.S. service members had returned to their duties after having been evaluated for traumatic brain injuries (TBI), an Iraqi official was also injured in the blasts.
U.S. officials anticipate the possibility that additional service members could step forward with TBI symptoms.
There have been more than 150 rocket and drone attacks on U.S. bases in Iraq and Syria since mid-October carried out by Iranian-backed militias claiming they are in support of Palestinians in the Israeli-Hamas war in Gaza.
But their use of ballistic missiles, as happened this weekend was seen as an escalation.
There are still about 2,500 American troops serving in Iraq and 900 in Syria to prevent a resurgence of the Islamic State.
However, the continued presence of American troops in Iraq was cast into question by Iraq's parliament shortly after a U.S. drone strike on January 4 that killed a top leader of one of the Iranian-backed militia groups responsible for the attacks on U.S. forces.
That drone strike and other retaliatory strikes carried out inside Iraq and Syria have so far not deterred the groups from continuing to launch the attacks.
The attacks are a sign of rising tensions in the region for the United States which has also carried out retaliatory strikes in Yemen targeting Houthi militants responsible for more than 30 attacks on commercial shipping in the Red Sea and the Gulf of Aden.
Most recently on Monday, the United States and United Kingdom carried out another major strike against Houthi locations associated with the shipping attacks.
It marked the eighth retaliatory airstrike carried out against Houthi targets since Jan. 11 which U.S. officials say have degraded the Houthis ability to carry out the attacks even as they have continued to do so.
This is a developing story. Please check back for updates.