Are we aiming for a cleaner kill? Eleven years ago an international agreement banned landmines. This week Britain joined more than 100 countries forswearing cluster bombs. True, we are not quite living a John Lennon lyric, but it would be churlish to deride the optimism of campaigners who welcome this step-by-step approach to making warfare a more discriminating business.

Such agreements invariably produce equal measures of hyperbolic expectation and worldly scepticism. So it was in 1899 when all the great powers met in The Hague to discuss prohibiting the most unpleasant weapons of war. The doughty peace campaigner Baroness Bertha von Suttner was sure the opening session would prove an “epoch-making date in the history of the world”. With a more knowing air, Theodor Mommsen, an eminent German historian, believed it would be remembered as “a printer's error in the history of the world”.

That the assembled militarists would turn their swords into ploughshares was certainly fanciful. After all, the conference was the idea of the Tsar of Russia, who the Germans suspected was merely trying to get round his guns being smaller than their guns.

The detached air of the delegates in the opening negotiations hardly suggested they were serious. However, as the discussions dragged on, so the throng of peace campaigners and reporters waiting expectantly outside began to play on the minds of the representatives. Mass petitions were handed in. There was even a poem from the Queen of Romania written under her pen name, Carmen Sylva.

Thus while the general disarmament talks were successfully sidelined by the need for “further serious study” and a court of arbitration was devised that lacked teeth, genuine efforts were made to outlaw those weapons that seemed particularly frightful.

The result was a series of declarations in which the big powers agreed not to use either expanding “dum-dum” bullets or asphyxiating gas against each other. Also ruled out was the novel practice of dropping bombs from balloons, which was condemned as an unwarranted danger to innocent civilians on the ground.

The prohibition was set to expire after five years but was renewed by a second Hague conference in 1907. A further renewal was intended for a date in 1915. Instead, that was the year the Germans first unleashed chlorine gas attacks on the Western Front. When the British and French protested that this breached the solemn undertakings at The Hague, the Germans claimed that only chemical shells had been prohibited, not their chosen means of gas delivery.

In war there is not just atrocity. There is the legal loophole.

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