NATO’s large-scale military exercise, named Nordic Response 24, which will last until March 15, involving 20,000 soldiers from 13 states in the northern regions of Finland, Norway and Sweden.

They are participating in the exercise, under the command of Norway more than 4,000 Finnish soldiers.

“For the first time, Finland, which shares a border of 1,340 kilometers with Russia and joined NATO in April 2023, will participate as a NATO member country in the exercise of collective defense of the alliance areas,” the Finnish defense forces said in a statement.

The Swedish armed forces said about 4,500 people from the Air Force, Army and Navy will take part in the exercise, which is being conducted in demanding Arctic winter conditions.

Both Sweden and Finland had developed strong ties to NATO after the end of the Cold War, but public opinion remained firmly against full membership until Russia’s invasion of Ukraine.

Non-alignment was seen as the best way to to avoid tensions with Russia, their powerful neighbor in the Baltic Sea region. But the Russian attack caused a dramatic shift in public opinion in both countries, and they jointly applied to join NATO in May 2022.

The pan-Scandinavian exercise is part of Steadfast Defender 24the largest NATO exercise in decades, involving up to 90,000 soldiers for several months aimed at showing that the Alliance can defend its entire territory up to its border with Russia.

All NATO members are participating in the Steadfast Defender 24 exercise, which will last until May 31.