It was enough.

One weakness of the JN25 code was not a weakness of the code itself. It was the formalities with which Japanese officers addressed each other. With some idea what ranks the sender and receiver were, the code folks could get a few words to start with.

Of course, the diplomatic code (American title "Purple") was also extremely secure, and based on a machine. No machine was ever captured, any to be abandoned were pounded into sand.

The crypto folks knew they needed the machine, so they figured out how it probably worked and built one. It worked. The Japanese were told the code was broken, but were certain that was just a deception, Americans were far too stupid to break it - they didn't really know the truth until testimony before Congress.

Only one small piece of a Purple machine was ever found, in the ruins of the Japanese embassy in Berlin. It turned out the American machine was based on the exact same model of telephone switch as the Japanese original.

Japanese propaganda, which they came to believe without question, was that Americans were really stupid. When the bomb went off over Hiroshima, the guy in charge of Japan's nuclear bomb program says he recognized what it was instantly, but wondered, "How could the Americans develop the bomb?"

Of course, he was waiting for a shipment of enriched uranium from Germany, but the U Boat was captured. The Japanese officers on board immediately committed suicide. The uranium was eventually delivered to Japan. Uranium short Americans used it in their bombs.