Cable-cutting in preparation for war - the historical precedent.

From Page 2 of The Z gram intercept: greatest cryptography coup of World War I

At the outset of the war, the Germans had five transatlantic cables that ran through the English Channel. One went to Brest in France, another to Vigo in Spain, one to Tenerife in North Africa and two to New York via the Azores. The English cable ship Telconia cut them all in England's first offensive action in the war. This left a cable that ran between West Africa and Brazil that was largely American-owned that the Germans could use. In short order the allies ended that source of direct cable communications with the overseas world. Consequently, Germany was forced to use their powerful wireless station at Nauen, just a few miles outside Berlin. From this moment, German messages were routinely picked from the air and began pouring into the offices of British Naval Intelligence. In order to capture this flood of information, four new allied listening stations were established along the English coast with direct wires to Admiral Hall's offices. The positive result from this investment could not be overemphasized.