The Fourteen Part Message is one of many myths that have taken root on the Pearl Harbor attack. It fits into many of the narratives of the engagement, with Yamamoto--the noble enemy commander--determined that the attack should not be a surprise, and that the delay in receipt of the message was a critical failure on the Japanese part that made the attack an illegal sneak attack prior to the start of the war.

However, it's critical to note that the Fourteen Part Message did not in fact contain a declaration of war on the United States by Japan. You can read the whole Fourteen Part Message here. Reproducing the final parts of the message in full is quite revealing:

Obviously it is the intention of the American Government to conspire with Great Britain and other countries to obstruct Japan’s effort toward the establishment of peace through the creation of a new order in East Asia, and especially to preserve Anglo-American rights and interests by keeping Japan and China at war. This intention has been revealed clearly during the course of the present negotiation.

Thus, the earnest hope of the Japanese Government to adjust Japanese-American relations and to preserve and promote the peace of the Pacific through cooperation with the American Government has finally been lost.

The Japanese Government regrets to have to notify hereby the American Government that in view of the attitude of the American Government it cannot but consider that it is impossible to reach an agreement through further negotiations.

You'll notice something critical here: there is no declaration of war contained in the message. The language taken by Japan is clearly very strong, and it does declare that Japan no longer believes in continued negotiations with the United States. It could definitely be interpreted as a strong sign that Japan was moving towards war, but that does not change the fact that nowhere in the message does Japan declare war against the United States, Britain, or any of the other Allied powers. Nor did the United States see the Fourteen Part Message as an official declaration of war. In the famous "Day of Infamy" speech, President Roosevelt says:

While this reply stated that it seemed useless to continue the existing diplomatic negotiations, it contained no threat or hint of war or armed attack.

The "official" Japanese declaration of war came from a Privy Council meeting in Tokyo at 3:15 pm December 7, Pearl Harbor time, nearly seven hours after the launch of the attack. The release of this declaration was not tied to the translation or decryption staff of the Japanese embassy in Washington, but it was still released well after the launch of the attack. While it would be reasonable for any government in receipt of the note to begin to see war as a much more immediate concern, the Fourteen Part Message simply was not a declaration of war.

So why has the Fourteen Part Message become such a fixture of pop-culture depictions of the Pearl Harbor attack? As you mentioned, in Tora, Tora, Tora, the race to deliver the Fourteen Part Message is a point of major drama, and the failure to deliver it a key point in why the Pearl Harbor attack so enraged the American public. The answer likely comes back to the great late historian Gordon W. Prange, who was a historical advisor to the film, and whose works on Pearl Harbor have become the origin point of many of the myths and legends surrounding Pearl Harbor. I say this not to overly disparage Prange, as he is a fine historian who did excellent research for this book. Rather, the works are simply older at this point, and additional discussion and analyses of the events have come to pass since then. Prange makes the delivery of the Fourteen Part Message into a major piece of drama, which was then replicated on the silver screen with Tora, Tora, Tora. And indeed, it is good drama. The combination of these two helped to cement the image of a Japanese typist slowly writing out the message even as Japanese aircraft make their way to Pearl Harbor as a key part of the cultural memory of the Pearl Harbor attack.

There's also a certain element of lionization of Admiral Yamamoto Isoroku involved. US popular culture likes to present Yamamoto as the brilliant, but noble, enemy commander who--while disagreeing with the war--sought to fight for his country as best he could. Whether this reputation is deserved is a topic for an entirely different post, but suffice it to say, opinion of Yamamoto among historians is not so lofty. By making the surprise attack at Pearl Harbor the fault of some nameless typist or coder at the embassy in Washington, Yamamoto's own reputation is preserved. Instead of launching a sneak attack which so enraged the American public that "revenge" for the attack became a key part of later decisions related to unconditional surrender, Yamamoto gets to remain a noble figure, who tried his best to avoid a sneak attack, yet was foiled by the limitations of another. This, of course, ignores that Yamamoto had been violating American, Filipino, and Malayan territorial waters and air space well before the message was supposed to have been delivered, with the midget submarines even attempting to penetrate Pearl Harbor well before the Fourteen Part Message was supposed to be delivered. Any of these could have bee construed as an act of war, and they are hardly the actions of a commander determined to avoid hostilities until just after a declaration of war was submitted.

Suffice it to say, the importance of the Fourteen Part Message is overstated. While it makes for good viewing material in a tv documentary or feature film, much like Yamamoto's attributed "sleeping giant" quote, it is not necessarily good history.

Hope this helps to answer your question, and please let me know if you have any follow ups.

Sources

• Gordon W. Prange, At Dawn We Slept: The Untold Story of Pearl Harbor

• Alan D. Zimm, The Attack on Pearl Harbor: Strategy, Combat, Myths, Deceptions

This is a good question, particularly in light of how often the 14-part message is misremembered, misrepresented, or misunderstood in the telling of the story about Pearl Harbor.

For starters, the 14-part message did not contain a declaration of war or even an ultimatum from the Japanese. An example of an ultimatum, in this context, would be Great Britain's response to the German invasion of Poland in 1939: "I am accordingly to inform your Excellency that unless the German Government are prepared to give His Majesty's Government satisfactory assurances that the German Government have suspended all aggressive action against Poland and are prepared promptly to withdraw their forces from Polish territory, His Majesty's Government in the United Kingdom will without hesitation fulfill their obligations to Poland."

Basically: "Get out of Poland or we will declare war on you."

The Japanese 14-part message falls well short of that. You can read the full text of the message here. If you'd rather not read it, it is mostly an accounting of Japan's grievances with the United States after their failed negotiations and responses to the developments of the events leading up to the attack. It does not even fully break off diplomatic negotiations with the United States, though it comes very close at the very end.

I assume you're also referring to the Hague Convention, and not the Geneva Convention. The Geneva Convention was laid out mainly for the protection of prisoners of war, and Japan had only ratified part of it. The Hague Convention of 1907 (to which Japan was a signatory) states, among other things, that "The contracting Powers recognize that hostilities between themselves must not commence without previous and explicit warning, in the form either of a declaration of war, giving reasons, or of an ultimatum with conditional declaration of war." Anyway, Japan's 14-part message doesn't fulfill that requirement.

The Japanese never intended to provide advance warning to the United States before the attack. Even if the message had been delivered 30 minutes before the attack commenced, it did not have explicitly warn that hostilities were about to commence. It is sometimes suggested that the American government would have been braced for the attack if the message had been delivered on schedule, but even that is likely not true. The American intelligence operation in Washington intercepted and decoded the first 13 parts of the message late on December 6 (the 14th part was transmitted later) and had delivered it to President Roosevelt before he went to bed. While the final section of the message was a strong indicator that Japan was done with its diplomatic efforts, the Americans were smart enough to know what was coming. Roosevelt, upon reading the 13 parts that he did have, reportedly handed it to an aide and said "This means war." The confusion often comes because Pearl Harbor itself didn't receive any information about this message until it was too late. Washington had the message hours before the Japanese delivered it; Hawaii did not.

The exact motive or motives behind the 14-part message may never be fully clear. One certainty is that both the Americans and Japanese were playing for time by November of 1941. The Americans had started their military mobilization in 1940 (earlier, in some ways) and the US military was busy fortifying its positions in the Pacific, training draftees, and building ships by late 1941. Every additional week the US could delay the war would help it to send more planes and guns to the Philippines, Wake Island, Guam, and other outposts. It was more time to build up the Army and Navy, and more time that Britain could continue to draw resources from its colonial holdings in the Indo-Pacific. The Japanese were also playing for time; there was little hope for negotiations by September or October, when the decision was made to attack Pearl Harbor. But the Japanese needed time to train their air crews (2 of the aircraft carriers were brand new), and to organize their attacks around the Pacific.

It has been suggested that Admiral Isoroku Yamamoto demanded that the Americans receive a final notification from Japan's diplomats before the attack. Yamamoto's strategy by attacking Pearl Harbor was to deliver a knockout blow to the American fleet that could prevent any counterattack on Japan's advances in the Pacific. He hoped that by destroying the fleet at Pearl Harbor, Japan would have enough time to consolidate and reinforce its holdings in the Pacific to make any American counterattack in 1942 or 1943 unpalatable given the high level of casualties it would take to attack the new Japanese territory. This would lead the Americans to sue for peace, leaving Japan to its devices. Yamamoto had lived in the United States for a few years earlier in his career and was familiar with the American people. He believed some kind of pre-emptory message might ameliorate the anger that he knew he would incur with a surprise attack that occurred without a declaration of war. Yamamoto was reportedly crestfallen when he learned that the diplomatic message had been delivered too late.

Of course, we may never know if that is true or not. Yamamoto was killed in 1943 and thus was not alive to be interviewed after the war or potentially tried for war crimes as the architect of the Pearl Harbor attack. I'm not an expert on Yamamoto, but I don't believe any diary entries or writings from Yamamoto definitively state whether it was his intention to have the message delivered before the attack. Yamamoto has taken almost mythological status over the last 80 years, and some historians who have sought to write biographies on him have reported that his family continues to closely guard his legacy and public image. I'm not sure we'll ever get a critical biography on Yamamoto like you might see with an American figure like Douglas MacArthur, whose public perception has changed significantly thanks to the study of historians. Regardless, the plan was predicated on surprise and would not have been nearly as effective if the US military on Oahu had even 10-15 minutes of advanced warning. Pearl Harbor was always intended to be a surprise attack and the 14-part message would not have changed that.

Sources: As always, "At Dawn We Slept" by Gordon Prange is an excellent starting point to understand the diplomatic, military, and strategic preparations leading to Pearl Harbor, including the 14-part message. Tora! Tora! Tora! is largely based on this book.

John Toland's "The Rising Sun" provides more background to the Japanese side leading to Pearl Harbor, particularly the inter-governmental struggles for power between hawks and doves within the Army, Navy, and foreign ministry.

"Yamamoto: The Man Who Planned Pearl Harbor" by Edwin Hoyt is actually light on the information about Yamamoto's planning of Pearl Harbor but is at least a widely available biography of the admiral.