Proving Grounds is the first Co-op mission in Call of Duty: 1945. It is the Soviet assault on a German testing site housing a powerful enemy
The level begins with the player in a JS-1 tank outside of a German testing facility. The players must fight their way through several squads of German AT soldiers to get in. Once in the players must face a Maus. The Maus is extremely strong, requiring dozens of hits to be destroyed, and can kill the players JS-1s with a single shot from it's 128mm gun. After destroying the tank, the level ends.
Untouchable, 20G- Enter the base without taking a hit from a German rocket.
Not Today 30G- Destroy the Maus without taking any casualties.