Two helicopters faced off against an F-15D Eagle fighter aircraft above water in an unprecedented combat defense test conducted by the Air National Guard, Air Force Reserve and U.S. Navy.

The test saw an HH-60W Jolly Green and an HH-60G Pave Hawk defend against attacks by an F-15D in a maritime setting.

The attacks were staged to simulate real-world scenarios in which U.S. rescue helicopters were fired upon at sea.

“The HH-60W has never undergone this type of evaluation. This test data will help us determine how effective U.S. countermeasures are against fighter aircraft over water,” U.S. Air Force Lt. Col. Don Smith, AATC HH-60 Division deputy director, said in a service release.

Two Air National Guard units from California took part in the tests, with the F-15D flown by Guardsmen of the 144th Fighter Wing and the HH-60G Pave Hawk piloted by Guardsmen of the 129th Rescue Wing.

The HH-60W Jolly Green helicopter belongs to the Air Force Reserve’s 305th Rescue Squadron based in Arizona.

This test was the first of its kind, and will provide a basis for improving the survivability of rescue helicopters should they come under attack by enemy air forces.

The exercise comes amid increasing focus on training U.S. units for maritime operations in the Indo-Pacific. This month, the Air Force conducted a month-long series of exercises in the Indo-Pacific in what was the largest-scale exercise of U.S. airpower in the region since the Cold War.