I'm listening to Fluckey's "Thunder Below" about the USS Barb's exploits. He mentions a mission to shell a Japanese "cable station" in the Kuril Islands, but doesn't explain what it is for. He does mention that the consequence of a successful attack would mean that Japanese ships would be forced to rely more on radio communications, enabling US eavesdroppers.
So I'm deducing it's a cable as in a physical cable link for communications - an undersea cable relay of some kind? But how would that help ships? Or is the idea that with the cable station in place, they could broadcast on a shorter-range set and then the communication would go the rest of the way via secure hardline, while without the cable station they would have to use longer-range broadcasts that were more vulnerable to eavesdropping by US codebreakers?