What were Germany's and Japan's best naval decisions?

What were Germany's and Japan's best maritime decisions during the war?

Japan's coordinated opening attacks bought time, while Germany's invasion of Norway created its most valuable maritime advantage.

The best decision for both Axis states would have been to avoid the war, but the question asks what worked once they chose it. Japan's attack on Pearl Harbor, combined with rapid blows against Hong Kong and Singapore, bought roughly six months in which its forces could expand. Germany's strongest naval decision was the invasion of Norway. The operation should not have succeeded, yet possession of the coast created a durable strategic advantage. The answer judges decisions by the freedom of action they created rather than by whether the larger wars were winnable.