NATO forces took part in drills in northern Poland on Friday, an area of crucial significance to the security of the alliance's eastern flank.
The Suwalki Gap, a sparsely populated area of Polish territory lying between Belarus and the Russian exclave of Kaliningrad, is of strategic importance because its takeover by Russia would isolate the Baltic states from the rest of NATO.
Poland has been beefing up its armed forces in response to Russia's invasion of Ukraine and plans to raise defence spending to 3% of gross domestic product (GDP).
"As part of these drills there were exercises that... were formulated based on our experience and observation of the battlefield in Ukraine," said Polish Defence Minister Mariusz Blaszczak. "We know what methods Russia uses and what methods (of defence) are effective."
The TUMAK- 22 exercises involve 2,000 soldiers from land and air forces, the Polish Ministry of Defence said. They also involved more than 1,000 pieces of combat and logistical support equipment.
On the snowy day, drills included practicing crossing water and landing. Explosions rang out at Lake Kepno near the village of Klusy as a simulated attack began.
"What happened today at Lake Kepno was part of a larger exercise which has been going on for several weeks," said Colonel Tomasz Biedziak.
The drill saw dozens of Polish and allied soldiers cross the water with military vehicles on amphibious transporters, while U.S. troops in Abrams tanks simulated chasing the enemy.
Low clouds prevented military aircraft from taking part at Lake Kepno.