Dutch soldiers are conducting a large-scale exercise in Norway this week to simulate repelling invading Russian forces, a mission their commander describes as more than training, calling it a “rehearsal.”

Starting Sunday, Norway and a dozen allied nations are practicing as if they must expel an invading force—intended to represent Russia. Dutch marines will land on the icy and inaccessible Norwegian coast to disable cruise missiles and air defenses meant to keep NATO at bay. They will then attack the invading troops from the flank while the allied main force advances elsewhere.

Commander George Pastoor, speaking to ANP from the amphibious transport ship Johan de Witt, said the operation is part of NATO’s Cold Response exercise, which the Netherlands has participated in before. “We are much more aware now that it might not stay just an exercise,” Pastoor said. He noted that Russia’s main naval bases lie close to northern Norway, and in a real conflict, Moscow would seek to protect access to the open sea.

This year’s exercise is not only unusually large, spanning from Lithuania to the Arctic, but also more serious than before. “I call it a ‘mission rehearsal’ when I stand in front of the troops,” Pastoor said. Previously, mainly field units trained, but now commanders are more involved and must consider the political and civilian consequences of their actions, including the impact on society under wartime conditions.

“If a Russian submarine passes the North Cape, you are really looking straight at the port of Rotterdam. There is nothing in between,” he said. “The Russian navy would have the heart of Western Europe in its sights and could cut critical links with the United States.”

The exercise is also a severe test for marines operating in extreme conditions of snow and ice. “This year may be even harder, in wet snow that soaks everything and freezes overnight. It’s extreme. Then it’s a matter of survival,” Pastoor added.