NATO has begun its largest military exercises since the Cold War as the West tries to keep up with Russia's growing military presence.
About 50,000 soldiers, 250 aircraft, 65 ships and 10,000 tanks will take part in the Trident Juncture war games, which have began at various locations across northern Europe.
With 31 countries involved they are designed to test NATO's response to an attack on Norway, where most of the drills are taking place.
Footage showed military vehicles barrelling down muddy forest tracks, soldiers marching through barren landscapes and fighter jets taking off from remote runways.
While the notional enemy has been dubbed "Murinus", a "fictional near-peer adversary on the north-eastern flank of the Alliance", the focus of the drills have not been missed by Russia.