Secure cable links improve early warning

An undersea telegraph cable would let a Helgoland garrison pass observations quickly back to Britain without broadcasting by radio. That would make the island an early-warning post as well as a weapons platform. An attacker trying to silence it would first need to discover where a cable entered and left the water, then reach it in difficult seabed conditions. Britain also possessed cable-laying ships and could use multiple routes, making a complete communications cut harder than severing one known line.