The U.S. Defense Department on Tuesday named four of the six U.S. soldiers killed by an Iranian drone strike, the first U.S. casualties of the war with Iran that President Donald Trump launched over the weekend.

Army Reserve soldiers Capt. Cody A. Khork, 35, of Winter Haven, Florida; Sgt. 1st Class Noah L. Tietjens, 42, of Bellevue, Nebraska; Sgt. 1st Class Nicole M. Amor, 39, of White Bear Lake, Minnesota; and Sgt. Declan J. Coady, 20, of West Des Moines, Iowa, died March 1, a Pentagon statement said.

All were assigned to the 103rd Sustainment Command in Des Moines. They were killed during a March 1 drone attack on a commercial port in Kuwait, a U.S. ally. 

The Defense Department has not released the names of the two other soldiers killed in the strike. The incident remains under investigation, the statement said.

The Pentagon did not mention Iran, but said the soldiers were supporting Operation Epic Fury, the administration’s name for the operation.

Trump and Cabinet officials have struggled since Saturday to articulate a cohesive rationale for the strikes, which U.S. forces conducted with Israel. 

Trump said Tuesday he “forced Israel’s hand” to launch the joint attack, contradicting Secretary of State Marco Rubio’s explanation a day earlier that the U.S. joined an Israeli operation.

The incident marks the second time in a matter of months that Iowa service members have been killed in the Middle East.

A lone gunman associated with ISIS killed two Iowa National Guard members, Sgt. William Nathaniel Howard of Marshalltown and Sgt. Edgar Brian Torres-Tovar of Des Moines, in Syria in December.