Two U.S. F-22 stealth fighter jets squared off in simulated dogfights with two of Norway’s expanding fleet of F-35 aircraft Wednesday as part of an exercise aimed at strengthening the NATO alliance and increasing its deterrent power.

The two U.S. F-22s are among 13 in Europe for a series of short-term deployments in places such as Greece and Poland, with further training missions planned in undisclosed locations in coming days.

The Norwegian deployment lasted one day but will lay the groundwork for NATO allies as they work to integrate their stealth warfare capabilities, Colonel Leslie Hauck, chief of the fifth generation integration division at the U.S. Air Force’s headquarters in Europe, told reporters in Norway.

The deployment is part of U.S. efforts to reassure European allies after Russia’s 2014 annexation of Crimea.

F-35s arriving in Europe

Growing numbers of Lockheed Martin Corp F-35s are arriving in Europe as the world’s most advanced warplane and most expensive weapons program matures following a raft of cost increases and technical challenges in its early years.

“Every training opportunity that we have betters our readiness for any potential adversary of the future,” Hauck said at the Orland air base, home to six of Norway’s expected 52 F-35s.

Hauck leads a new office at Ramstein Air Base in southwestern Germany, that is working to ensure a smooth transition for about 40 F-35s scheduled to be in Europe by year’s end. The first of which are set to arrive in 2021.

Next month, a group of senior officials from the United States and seven other F-35 operator countries — Norway, Denmark, Italy, Turkey, Israel, Britain and the Netherlands — will meet to compare notes on the new warplane, which was first used in combat by Israel in May.

Better battlefield overview

The United States has more than 150 of the aircraft, whose sensors pilots say give them the most extensive overview of a battlefield of any combat jet available.

Norwegian Air Force Major Morten Hanche, who piloted one of the Norwegian F-35s, said the mock fight with the F-22s was great practice, especially since the F-35s generally surprise and overpower other nonstealth aircraft.

He declined to name the winning aircraft, saying only: “The F-22 is a very formidable opponent.”