Yes, too bad that even the Japanese were late decoding the message to their diplomats in Washington, DC. That blows your theory about Marshall right out the window.
Your argument makes no sense. How does the fact that the Japanese embassy staff were late in translating the 14-part message into English refute his theory about Marshall? We know, and even the JCC admitted, that FDR and his advisers had the first 13 parts of the 14-part message on the night of 6 December, and that they had the entire message plus the two accompanying instruction messages by no later than 9:00 AM on 7 December.
When the final segment of the 14-part Japanese diplomatic cable and the associated instructions were decrypted on the morning of 7 December, the White House and senior military officials knew they had to send some kind of warning to Kimmel and Short. They knew they would be unable to come up with a believable excuse for not giving Kimmel and Short some kind of warning about the Japanese message. However, the warning they sent was not only vague but was sent via regular commercial telegraph and did not arrive until hours after the attack.
Marshall told the Roberts Commission that he sent the warning message via telegraph because he was afraid the Japanese would overhear a warning given over the scrambler phone.
Marshall’s explanation is nonsensical and unbelievable. It is hard to fathom what intelligence Marshall believed would be revealed if he simply called Short and ordered him to put the island's military forces on full alert immediately. Such a warning would not have revealed that Japanese codes had been broken and would have rendered the Japanese attack far less effective. Or, Marshall simply could have given Short any number of believable cover stories for putting the forces on alert, such as that an American spy in Tokyo had learned that a Japanese fleet would attack Hawaii or that Russian fishing vessels had spotted a large Japanese fleet heading east, etc., etc.
Marshall could have easily warned General Short on the scrambler phone without mentioning Japanese intercepts. Incredibly, Marshall did not even have the warning sent as a priority message and failed to ensure that it was marked as urgent.
Moreover, as mentioned, Marshall's "warning" was hardly worthy of the term. It did not even order Short to increase his alert status, or even suggest that he consider doing so. Marshall could have much more easily given this vague "warning" over the scrambler phone. But, of course, Short may have asked for asked for clarification and may have asked Marshall if he should put his forces on full alert, etc., etc., so Marshall could not risk conversing with Short about the Japanese message.
Marshall's "warning" also contained the lie that no one knew if there was anything important about the time the Japanese set for the delivery of their message, when in fact we know that virtually everyone who saw the message recognized that the 1:00 PM time was the time the attack would occur.
Marshall could have had no rational, credible fear of Japanese monitoring and thus no reason to avoid sending this critical warning via the fastest possible means, especially given the fact that he knew time was of the essence. Even if he believed the Japanese would overhear the warning, why would this have persuaded him to send the warning in such a format that it would likely arrive too late to do any good? Indeed, if the Japanese had been monitoring the scrambler phone (they were not), they would have realized they had lost the element of surprise and may have even called off the attack. Was Marshall just too dumb to understand this obvious fact?
If nothing else, warning Kimmel and Short via scrambler phone or Navy radio would have given them time to get more men and guns ready to respond when the attack occurred. The Navy Court of Inquiry noted that "had the telephone and plain language been used, this information could have been received in Hawaii about two hours before the attack began" (NCI 318). Two hours would have given Kimmel and Short ample time to get most of their planes in the air and to have many more men and guns ready for action. It is difficult to believe that these obvious, common-sense considerations did not occur to Marshall.