With the right investments, Marines at expeditionary advanced bases in Norway, Iceland and Greenland could create what the commandant referred to as an anti-submarine warfare fence that would bottle Russian submarines in the Norwegian Sea, keeping them out of the North Atlantic.
The same concept could be applied to the First Island Chain in the western Pacific. Close, confined seas may offer more opportunities for Marines to sense and strike Chinese ships and submarines.
Marine expeditionary advanced bases could also assist Navy aircraft that currently hunt for submarines, such as the P-8 Poseidon, providing air defense and combat air patrol. The aircraft could stop off at forward-postured Marine bases until Navy ships move into position.
※combat air patrol:
Fighters flying a tactical pattern around or screening a defended target, while looking for incoming attackers.
Combat air patrol aims to intercept and destroy hostile aircraft before they reach their target.