The attack on Pearl Harbor was a surprise military strike by the Imperial Japanese Navy Air Service against the United States naval base at Pearl Harbor, Hawaii Territory, on the morning of December 7, 1941. Newspapers.com

I'm very aware of the fact that "the winners write history", but still, this is something which used to baffle me even as a naive child. Why on Earth are they emphasizing the fact that the Pearl Harbor strike was a "surprise" or somehow "cowardly"?

Am I still naive? Has any military power in the history of mankind told the enemy in advance about their plans to attack them, so that they would get a "fair chance" to defend themselves? I cannot imagine that this has ever been the case, but who knows? Nothing about this world surprises me anymore. Maybe that was considered some kind of "code of honor" for hundreds of years or something.

It just sounds ridiculous to me. Of course a military strike would be kept secret for as long as possible. Ideally, from the attacker's point of view, they (the enemy) would never have a clue about their impending attack until the bombs actually started falling.

So why, specifically in relation to Pearl Harbor, do they make it out to be such a big deal that it was a "surprise"? What did they expect? A telephone call from the Japanese general in charge, saying:

Oh, yes, by the way: tomorrow at so-and-so time, we'll be air-bombing Pearl Harbor, so make sure to regroup and wait for us so that we can be shot down before we reach your base!

? I don't get it.

(Sorry if this is somehow offensive to somebody. Whenever anything related to WW2 or other recent wars is mentioned, there's always the risk of upsetting people.)

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    every ultimatum is a warning "Do X or it is war! You have until such day/time". Including the UK/French ultimatum to Germany when Germany invaded Poland. Some people in just to become enemy countries even had enough time to run home. If the ultimatum is based on a previous alliance or guarantee, you can even argue that the enemy had to see it coming.
    – Luiz
    Commented Feb 17, 2020 at 18:06
  • 1
    Korea comes to mind. Many times military buildup is a signal that the nation is serious. If the attack comes after a military buildup, then it is less a "surprise".
    – MCW
    Commented Feb 17, 2020 at 18:22
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    The 1991 Gulf War is a very recent example, with a build-up by coalition forces from 2 August 1990. The air campaign didn't begin until 16 January 1991. Commented Feb 17, 2020 at 22:11
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    It's true that military leaders will always seek an element of surprise whenever they can (even in a widely expected battle that has been announced in advance). Pearl Harbor has possibly been called a “surprise” military attack because it was particularly successful at surprising American forces on a tactical level.
    – Relaxed
    Commented Feb 17, 2020 at 22:56
  • 5
    A formal declaration of war says nothing about any planned attacks. For instance, in WWII Germany declared war on the US a few days after Pearl Harbor, but never carried out any significant attack on US territory - and indeed, lacked any practical capability to do so: en.wikipedia.org/wiki/…
    – jamesqf
    Commented Feb 18, 2020 at 4:00

5 Answers 5


It wasn't "cowardly or sneaky" of the Japanese to omit mentioning the date and time of their attack, it was "cowardly or sneaky" of the Japanese to start dropping bombs and shooting before they declared war.

At that time the rules of warfare required declaring war before starting to fight. A government was supposed to deliver an official announcement to the other government that there was a state of war between them, thus telling them that the hostile government forces might attack anywhere and anytime they considered desirable. And after delivering the message the country that declared war was free to begin attacking.

In this case the Japanese ambassador did not deliver the declaration of war in Washington DC until hours after the first bomb dropped and sometime after the government in Washington was informed of the attack on Pearl Harbor.

Article 1 of the Third Hague Convention in 1907 states:

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.


Japan signed the Hague Convention 18 October 1907 and ratified it 13 December 1911.

The United States of America signed the Hague Convention 18 October 1907 and ratified it 27 November 1909.


So Japan was legally bound to declare war before starting to fight the USA which was another contracting power of the Hague Convention.

Curiously, there is an law of war that can be interpreted as requiring a previous warning of a specific time and place of attack:

Article 25 of the Fourth Hague Convention in 1907 states:

The attack or bombardment, by whatever means, of towns, villages, dwellings, or buildings which are undefended is prohibited.


Clearly "attack or bombardment, by whatever means," would include attacks or bombardment by airships and airplanes in 1907, since the first Zeppelin flight was in 1900 and the first airplane flight was in 1903.

The next article, Article 26, says:

The officer in command of an attacking force must, before commencing a bombardment, except in case of assault, do all in his power to warn the authorities.


I interpret this to mean that it is forbidden to bombard, by whatever means as in the previous article, a town, village, dwelling or building, without warning the civilian authorities in the place, except when one's ground troops are actually assaulting the place.

If that is the correct interpretation, Article 26 was often violated in World War I, World war II, and other wars, where cities and towns were often bombarded by aircraft without warning given to the civilian authorities.

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    I know it's part of the US narrative that Pearl Harbor was "unfair" because there was no previous declaration of war. But, no offense or relativism intended, attacking without prior declaration of war, while not the norm, was far from being unheard of. Of course most of these attacks in WWII were by Axis forces (as they were the aggressors, globally speaking), but the Allies had their share of "surprise" attacks. Mers-el-Kébir springs to mind, the outbreak of the Anglo-Iraqi war, or the Anglo-Soviet invasion of Iran. In each of these cases, it was deemed "prudent" to not give advance warning.
    – DevSolar
    Commented Feb 19, 2020 at 9:51
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    @DevSolar The Anglo-Soviet invasion of Iran happened following an ultimatum, just as the Anglo-Iraq war. None of them were surprise attacks.
    – Greg
    Commented Feb 20, 2020 at 14:23
  • @Greg: Anglo-Soviet invasion of Iran: "The invasion was a surprise attack, described by Allied forces as rapid and conducted with ease. Prior to the invasion, two diplomatic notes were delivered to the Iranian government on 19 July and 17 August, requiring the Iranian government to expel German nationals. The second of the notes was recognised by the prime minister Ali Mansur as a disguised ultimatum." -- I.e., diplomatic notes (like the 14-part message), but no declaration of war, followed by a surprise attack.
    – DevSolar
    Commented Feb 20, 2020 at 14:31
  • Anglo-Iraqi War: "Still in contact with the British Embassy and with the approval of Ambassador Cornwallis, Air Vice-Marshal Smart decided to launch air strikes against the plateau the following morning without issuing an ultimatum; as with foreknowledge the Iraqi force might start to shell the airbase and halt any attempt to launch aircraft." -- Please provide sources for your assertion that these were not surprise attacks.
    – DevSolar
    Commented Feb 20, 2020 at 14:32

Declarations of war were normally made at the time via an ultimatum: "Unless you do something by date and time, then we shall be at war". This only says "we will be at war", it does not say anything about how the war will be fought. This was the form, for example of the British and French declarations of war on Germany in 1939.

The Japanese did not issue an ultimatum before attacking Pearl Harbor. The "14-part message" to the Japanese Embassy in Washington DC that the US decoded before the attack did not contain an ultimatum, although it did say that diplomatic relations were to be broken off. This was interpreted as meaning that attacks might take place, and warning was sent to US bases in the Pacific, but was not received at Pearl before that attack, owing to bad radio conditions.


You would issue a declaration of war to "legitimize" hostilities. Ideally, you trick the opposition into declaring a war they are ill prepared for... (Ems Despatch)

You would link that declaration of war to an ultimatum if there is hope that the opposition might yet step down from their position, and/or to further strengthen the impression that you really were given no other choice but the military option.

But there has been somewhat of a history of formal declarations of war being omitted in favor of achieving surprise (the kind which had become possible with the advent of highly mobile warfare):

  • Germany on Poland
  • Soviet Union on Poland
  • Soviet Union on Finland
  • Germany on Denmark and Norway
  • United Kingdom on Iceland
  • United Kingdom on Vichy France (Mers-el-Kébir)
  • Germany on Yugoslavia
  • United Kingdom on Iraq
  • Operation Barbarossa
  • Anglo-Soviet Invasion of Iran

...and half a dozen others listed elsewhere.

The interests of Japan and USA in the Pacific theater had been clashing for quite some while. The latest US embargo (25 July 1941) resulted in two options for Japan -- the military option (which would effectively necessitate neutralizing the US Pacific Fleet), or abandoning their empire. To this end, also see the Wikipedia article on the Hull note and the surrounding events.

The USA were definitely aware that hostilities were imminent. That the attack on Pearl Harbor happened without a formal declaration of war was convenient for the US narrative, and so was and is stressed whenever the subject comes up.


The question specific to Pearl Harbour had been answered by others: there was no declaration of war before the attack, and that is why it is called a "surprise" or "cowardly" and emphazised as such.

About other events where a country did notify an other about the war to come, largely before fighting actually occured, there is:

  • Gulf War (second, 1991): from August 1990 to January 1991, UN forces were deploying but did not fight against Iraqi forces until January.
  • 1948 war: Israel was threatened of war and actually invaded with not a lot of fights, because Arab countries did not know what they wanted to do actually. They started slowly and it gave some time to Hebraic defense forces to be organized.

To partly answer your question in the title: The first recorded account is the Thebans, allies of Sparta. Against Athen's ally Plataea, they launched a surprise attack without a declaration of war. That started the Peloponnesian War.

Given that mobilising an army took a very considerably time and effort before professional armies were created, any declaration of war would be just a vain effort to mask a surprise attack with a notion of chivalry.

As to the modern idea of regulating war, which is probably a result of the Treaty of Westphalia that constituted the first kind of world order: It may or may not have applied to Japan. I'm not deep enough into the history of international law.

  • 4
    The Theban attack on Plataea (429BC) did not start the Peloponnesian War (which began in 431). Commented Feb 19, 2020 at 23:05

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