TheCodeBreakers
destinations of Japanese convoys. Japan's conquests consisted almost
entirely of islands which could be supplied and reinforced only by sea,
and Nippon itself was an island empire.
American submarines therefore undertook in the Pacific what U-boats
were attempting in the Atlantic, and, as with the U-boats, cryptanalysis
helped them achieve their greatest successes.
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A direct line led from FRUPAC to the office of Captain R. G. Voge,
operations officer of the Commander, Submarines Pacific Fleet. The
Japanese convoys radioed the positions where they estimated they would
be as of noon on the next few days. This was to inform their own forces of
their locations, but FRUPAC solved the messages, and Jasper Holmes, an
ex-submariner himself, relayed them to Voge, who broadcast them to the
American submarines. This fattened their kill. Vice Admiral Charles A.
Lockwood, Jr., who was COMSUBPAC during most of the war, estimated
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