Asymmetrical warfare can involve attacking expensive ships with low cost uncrewed vessels.
Owing to the substantial superiority of the Royal Navy's surface forces, Germany's Imperial Navy (in World War I) and Kriegsmarine (in World War II) had little hope of sea control, but with submarines, the Germans hoped to choke off their access to seaborne commerce.
In both wars, the United Kingdom successfully resisted the German strategy with a combination of strict rationing and anti-submarine weapons and techniques.
During the Cold War, the Soviet Union invested heavily in submarines and would likely have pursued a similar strategy of sea denial had tensions with NATO escalated to open warfare.
The air force deploys assets to gather intelligence, conduct surveillance and reconnaissance and target ships with airborne weaponry.
The navy deploys sea mines, surface ships, and submarines in a layered defence and distributed lethality.