British flotilla defence placed destroyers and submarines around key ports, facilities, and the Grand Fleet. Cruisers protected trade and attacked enemy commerce, while the battle fleet sought control of the ocean and imposed blockade. Each arm covered a different operational problem, giving torpedo craft a useful role without asking them to win the war alone. Destroyers and submarines gained operational value from their place alongside the fleet's other arms.
Chapter · 19:12-20:49
Flotilla defence works as one layer of a balanced fleet
The British flotilla-defence model placed destroyers and submarines alongside cruisers and the battle fleet instead of treating them as substitutes for every other naval capability.