The United States launched a series of retaliatory missile strikes in Syria and Iraq on Friday. They were a response to a foreign drone attack on a U.S. military base in Jordan that killed three American service members.

At least three Arizona National Guard troops were medically evacuated from the base following the foreign attack.

Daniel Rothenberg is the co-director of the Future Security Initiative at Arizona State University. He’s unsure why Syria and Iraq were chosen as U.S. targets.

“We really don’t know because there’s many groups to potentially target. There’s lots of information about where these groups are but at the same time, we don’t really have a clear sense out here in the public exactly which sites were chosen and why," he said.

Rothenberg says the initial U.S. response was “measured” and that the Biden administration is proceeding with caution “to avoid escalation of the conflict.”