Iran’s killing of three additional U.S. service members has crossed a red line President Donald Trump has repeatedly drawn, forcing him to decide whether to escalate the existing campaign or take the far riskier step of expanding the conflict.

Over the weekend, first Lt. Tyler James Feehan of Hawaii and Pvt. Isabella Gonzales of Texas were killed in an Iranian attack on America’s Muwaffaq Salit Air Base in Jordan. A third service member was killed in Iraq by the “controlled detonation” of an Iranian drone. The latest casualties increase the total number of U.S. service members killed in action during the war to 17.