widespread view that some clarification in the law on the matter of the commencement of wars was called for.  But that easier said than accomplished. Various proposals were put forward.  One, by the Netherlands, would have imposed a requirement of a twenty-four-hour warning prior to the launching of any attack.  But the major powers – except for Russia – were opposed to that idea.  There was agreement, though, that, in the future, some kind of formal act should be required at the commencement of a war.  This idea was embodied in a Convention on the Opening of Hostilities.  The basic requirement was that “hostilities” now had to be preceded by a “previous and explicit warning,” which could take either of two forms: “a reasoned declaration of war” or “an ultimatum with conditional declaration of war.”

It cannot be said, however, that the Hague Convention was very successful in dealing with the issue.  For one thing, it left open the possibility that a declaration of war could be promulgated, with an attack then following immediately.  In material terms, this would hardly be distinguishable from an outright surprise attack.

Another difficulty with the Convention was that it was generally agreed that states retained the power to inaugurate wars without a declaration (or ultimatum), even if they no longer had the right to do so.  In other words, beginning a war in the Japanese fashion would now become a wrongful act (for parties to the Convention), but it would not actually prevent a state of war from existing.  It would merely subject the attacking state to some appropriate form of reparation to the defending one.

The problem of surprise attacks returned, with a vengeance, on 7 December 1941, when Japan attacked the American Pacific fleet at Pearl Harbor.  In this case too, negotiations had been in progress for some time – and had effectively broken down.  The previous day, 6 December, the American government had received Japan’s rejection of a set of peace proposals.  The reaction of President Franklin Roosevelt, to his close adviser Harry Hopkins, was that “[t]his means war.”

Interestingly, Hopkins immediately suggested that, since peaceful relations between the two countries were now over, the United States should attack first, to achieve the advantage of surprise.  Roosevelt demurred.  “No, we can’t do that,” he insisted.  “We are a democracy and a peaceful people.”  In taking this stand, Roosevelt was well aware that Japan was being left free to strike the first blow.  The time and place of that blow came as a surprise, but it can hardly be said that an attack of some kind was unexpected.

The question of the lawfulness of the Pearl Harbor attack in the light of the Hague Convention was raised in the Tokyo War Crimes Trials which followed World War II.  One of the counts alleged that the Pearl Harbor operation constituted treacherous killing by virtue of its having been launched in breach of the Hague Convention.  The prosecution contention was that killing done in the course of a violation of the Convention could not be regarded as a true belligerent action, but instead must be murder.  Seventeen of the defendants were indicted on that count.  The charge, however, was, in effect, dismissed by the tribunal, in favor of a more general charge of waging aggressive war against the United States.  As a result, there was no explicit ruling on the lawfulness of the Pearl Harbor attack per se.

For a perceptive discussion of this issue (and many more), interested readers should consult the fine book by Neil Boister and Robert Cryer, The Tokyo International Military Tribunal:  A Reappraisal (2008).  They take the view that the murder charges were misguided and therefore were correctly dispensed with – i.e., that the Pearl Harbor attack was a belligerent operation, involving secrecy rather than perfidy, notwithstanding that the war itself was, on the whole, an unlawful war of aggression.  But there continues to be room for dispute as to whether a state of war was actually in place prior to the actual attack, or whether the attack itself counted as a declaration of war, in the manner proposed by Hall.

The upshot is that attempts to guarantee that a razor-sharp line can be drawn between a state of war and a state of peace cannot be said to have succeeded.  There was always some scope left for fuzziness.  Since 1945, even the attempts at drawing such a line have been abandoned.  Declarations have war have gone largely – if not quite entirely – out of fashion.  In addition, the very idea of a state of war has lost its once-powerful grip on international lawyers and statesmen.  A world without states of war sounds, at first instance, like a blissfully peaceful one.  But alas, as we know all too well, that is not a fair description of the condition of our troubled planet.