If you could transport the war in the Middle East to the late nineties, a majority of people with a liberal temperament would have known what to do. They would say that the UN, the US, Europe or the Arab states must deploy troops to separate the two sides.

“We live in a world where isolationism has ceased to have a reason to exist,”

declared Tony Blair in Chicago in 1999, as he explained that global terrorist movements and the mass migration of refugees meant that the happy citizens of Europe couldn’t pretend that distant wars and failed states had nothing to do with them.

“Mankind’s suffering belongs to all men,” said Bernard Kouchner, the inspirational director of Medecins Sans Frontieres.

The humanitarian and political benefits men and women with guns on the ground would bring to Lebanon are obvious. An international force that meant business would stop Israelis bombing Lebanon and Hizbollah bombing Israel. Enforcing peace would answer what is now becoming a powerful argument against a wider Middle East settlement: whenever Israel removes forces from occupied territory — as everyone says it should — the abandoned land in Lebanon or Gaza Strip becomes a base for attacks from Hamas or Hizbollah.

The intervention of an international force could provide a model for how Israel might withdraw from the West Bank and also allow the government of Lebanon to assert its authority over Hizbollah’s state within a state. Finally, it would stop the world being distracted from the drive of Hizbollah’s patrons in Iran to get the bomb, which is the reason why this war started. Experience shows that troops would have to be ready for the long haul. In Bosnia, Kosovo and East Timor military interventions have dragged on for years, but the presence of foreign troops stopped mass murder.

Yet after Iraq, the phrase “humanitarian intervention” dies on the lips. Who would do it? The British and Americans couldn’t, their troops are committed in Iraq and Afghanistan.

The EU? The French just might, but overall the EU is deeply pacific.

The legacy of Iraq means that US, Arab or European generals would know that they would face suicide bombers. After what Iraq has gone through, few commanders would relish a mission in which they had to do a little more than smile and pat children on the head.

Iraq has had a further consequence that echoed in every discussion about war but find harder to pin down. Bush so enraged mainstream opinion that liberal-minded people trashed their principles. The legacy of their failure to support Iraqi democrats is a growth of conspiracy theory and a furious indifference to the suffering of others. Intervention in Lebanon, the Sudan or anywhere else would be “all about oil”, an “illegal” war or a neoconservative plot. Yet the need to rebuild a global consensus on what justifies the use of force won’t go away.

Blair told his audience in Chicago in 1999 that “threats to international peace and security” had to be the responsibility of the international community. In 2003, Bernard Kouchner told French citizens who were gloating about the success of the Islamists and the Baathists in Iraq: “Let us not imagine ourselves protected from barbarism.” Despite all that has happened since, they both remain right. — The Guardian