One of the most remarkable features of the "war on terror" - linguistically, and also politically - has been the warriors' characterisation of their target. They see terrorism as a barbarous attack on civilisation, a manifestation of "evil, the very worst of human nature", according to President Bush; it represents, in the words of two of his former senior colleagues, "no faith, no religion. It is evil, murderous" (Colin Powell) and "a cancer on the human condition" (Donald Rumsfeld).

A similarly absolutist view was expressed frequently by the former British prime minister, Tony Blair; and his successor Gordon Brown, widely praised for his government's more sober response to the abortive attacks in London and Glasgow on 29-30 June 2007, also described the would-be perpetrators as "evil".

In this view, terrorism is not a rationally apprehensible strategy (however repellent), adopted by real human groups for rationally apprehensible reasons (however repellent), but a malign force. Though it manifests itself through a bewildering array of local agents across the whole globe, it is essentially a single organism. Its rationale is literally incomprehensible. It is the embodiment of abstract, nihilistic hatred. It is aimed not at manifestations of actual worldly power or policy, but at the moral heart of western civilisation.

Charles Townshend is professor of international history at the University of Keele, England. Among his books are Terrorism: A Very Short Introduction (Oxford University Press, 2002) and Easter 1916: The Irish Rebellion (Penguin, 2005)

The conclusion of this line of thought is that terrorism aims to destroy peace, freedom, respect, dignity, and human worth; and that the fight against it is quite simply a struggle of evil against good.

It is hardly necessary to point out how much of the texture of reality is lost in such manichean fantasies. Whether the obfuscation involved is deliberate, or the product of deluded belief in an ability to see past surface complexity to an underlying simplicity, it takes its place in a long tradition of official exploitation of the natural fear and aversion that those who adopt terrorist methods provoke amongst the general public. It is worth considering how this obfuscation cripples any real public understanding of terrorism, and maybe even cripples the efforts of national and international bodies to develop effective anti-terrorist measures.

A tangle of ambiguity

Ever since terrorism was first identified as a threat, indeed, it has tended to evoke the same apocalyptic images. The purpose of terrorist violence was to shock and to disorient, and in this at least it has never failed. Auguste Vaillant, an anarchist who bombed the French national assembly in the 1880s, threatened "the deafer you are, the louder we must shout". Anarchism challenged the very basis of political order, and it was inevitable that states responded by denouncing anarchist terrorism as an assault on civilisation itself.

As today, it was often seen as essentially single - a "hydra-headed monster" in Victorian language. Even terrorist acts with much more localised aims could be viewed in the same way. The assassination of Archduke Franz Ferdinand at Sarajevo in 1914 was a nationalist protest, very far from representing an assault on the concept of the state, much less on the international order. Yet by precipitating the first world war (a consequence the assassin, Gavrilo Princip, can scarcely have imagined), it took on vast significance.

This became clear the first time the "international community", in the form of the League of Nations, tried to grapple with the threat of terrorism. In December 1934, two months after King Alexander of Yugoslavia was assassinated while on a state visit to France, the league recognised that "the rules of international law concerning the repression of terrorist activity were not sufficiently precise to guarantee efficiently international cooperation." Its attempt to rectify this situation occupied the next three years, as successive expert committees drafted an international convention (agreed at an international conference of the league in Geneva on 1-16 November 1937), and submitted to the body's general assembly in December.

Fred Halliday, "Terrorism in historical perspective" (22 April 2004)

Fred Halliday, "Terrorism and world politics: conditions and prospects" (18 January 2005

Fred Halliday, "Terrorism and its consequences: a tale of three cities" (16 March 2005)

Turi Munthe, "Terrorism: not who but why?" (21 July 2005)

Fred Halliday, "Terrorism and delusion" (12 April 2006)

See too the many articles in openDemocracy's "democracy & terror" category, and the daily security briefs, debates and articles in our focused sub-domain, terrorism. openDemocracy.net

The assembly's debate on the draft revealed insuperable problems that were enough not only to sink the 1937 convention, but to handicap international cooperation for decades. These problems go to the heart of our understanding - or lack of understanding - of terrorism.

The debate was framed in the familiar epic style: terrorism was a danger to "mankind as a whole", a contagion that threatened international peace and security, a threat to "the common heritage of the whole civilised world". But while there was general agreement at this rhetorical level, the question of defining terrorism itself was much more contentious. The convention aimed to create a new crime that would be extraditable: that would, in other words, not be seen as a "political crime".

It became clear, though, that several states insisted on retaining their freedom to offer political asylum. The most significant of these was Britain, and the British argument is worth noting. On the floor of the general assembly, Britain merely stated that accession to the convention would require legislation involving "departure from British traditions". Privately, it was clear that this meant a determination to protect the right of resistance - violent if necessary - to tyranny. ("If all states were at all times decently governed", a senior home office official noted, "anyone who attempted by force to overthrow an existing government should be a hostis humanae generis [enemy of the human race]. But when the government itself is a terrorist government, I think the person who endeavours to overthrow it by the only means available is not necessarily to be so regarded.") In other words - in a phrase that has acquired the status of formula - one state's terrorist might be another state's freedom fighter.

Although twenty-three states had signed the Convention for the Repression of Terrorism by mid-1938, Britain's refusal to do so effectively rendered it a dead letter. The failure to agree upon a definition of terrorism was to prove prophetic. There was a thirty-five-year interval until the League of Nations's successor, the United Nations, returned to the issue. When it did so in 1973, the UN set up three separate committees to (a) define terrorism, (b) examine its causes, and (c) propose preventive measures.

The failure of the first rendered the others pointless. The UN congress on crime prevention in 1975 noted that terrorism still had "no accepted definition in any legal code". The testy judgment of the terrorism expert Paul Wilkinson that the UN "has proved a broken reed on the whole subject of terrorism" once again highlighted the inability to agree "even on a basic working definition".

The same problem undermined the most recent surge of UN activity, in the wake of 9/11. On paper, UN 

Resolution 1373 (passed on 28 September 2001) was the organisation's most vigorous, and rigorous, effort to persuade member-states to enact anti-terrorist legislation. By January 2002 some 60% of UN members had "reported" - the very beginning of the process of compliance; a figure that then secretary-general Kofi Annan described (in what was itself an indication of the scale of the problem) as "unprecedented and exemplary". A year later, the resolution, under which a fifteen-member "counter-terrorism committee" had been established, was as dead as its predecessors. The same fate befell the hope that the Club de Madrid international summit on democracy, terrorism and security, convened on the anniversary of the Atocha bombings of 11 March 2004, would lead at last to a "comprehensive convention on international terrorism".

Critics of the UN's failures have no doubt that such a thing should be straightforward. "Terrorism must be outlawed under all circumstances and in all its forms", insists one recent demand that the UN finally get its act together. The blame for the fatal inability to agree a definition lies, in this view, with "Islamic states intent on wording that exempts the armed resistance against occupying forces" - i.e. against Israel. If that were the real reason, of course, the problem might have been solved before Israel existed.

But this is, in principle exactly the same issue as that on which Britain scuppered the 1937 convention. What resistance is to be deemed justifiable? Should all "terrorist crime" be taken outside the realm of political asylum? The cast of characters has changed: Britain, notably, has reversed its stance, and spent the half-decade after 9/11 discarding many of its traditional legal safeguards.  Its just-departed prime minister - a lawyer to boot - believes that the public's right to security outweighs the right of suspects to a fair trial, and that habeas corpus, the keystone of English civil liberties, could be permanently suspended. It is hard to overstate how dramatic a reversal of traditional English legal culture this represents. The mood music of the new government (including its home secretary), tested by a major security alert in its first days in office, is calmer and less alarmist; but it is too early to identify any halt to the trend established by its predecessor. 

In any case, if Britain had been prepared to abandon its safeguards in 1937, the world would long since have had an international anti-terrorism convention. Seventy years on, the world is no nearer to realising this aim.

A blind eye

Yet the problem of defining terrorism would still exist.  A likely consensus definition would go thus: "action intended to cause death or serious bodily harm to civilians or non-combatants, to intimidate a population or to compel a government to do or abstain from doing any act". That would, as is obvious enough, be a perfect characterisation of the United States's "shock and awe" air-bombardment campaign against Iraq. If we try to add provisos to head off such interpretations we get drawn into an ever thicker tangle of ambiguity.

At root, all official definitions of terrorism boil down to "violence we condemn". All attempts to go beyond the fundamental concept of murder are political, and few states will forgo their prerogative of interpreting such concepts. To achieve agreement among states on this is a Sisyphean task - precisely because terrorism is not a war of evil against good, not a fantastic hydra-headed monster, nor a disease, but a real political strategy adopted in myriad circumstances with myriad intentions. A surprisingly large number of states simply do not accept that it is a major threat. This may be because they are simply blind to the truth, or it may - just - be that they are keeping a level head.