Explanation:

- Option 1: Britain's invasion of Germany does not describe Operation Barbarossa; this operation involved Germany instead as the aggressor.

- Option 2: Axis invasion of Soviet Union is correct. Operation Barbarossa was the code name for Nazi Germany's invasion of the Soviet Union during World War II, launched in June 1941.

- Option 3: Japanese invasion of Manchuria is unrelated to Operation Barbarossa, as it was a separate event involving Japan and China.

- Option 4: None of the above is incorrect, as the operation specifically relates to the Axis invasion of the Soviet Union.