Earlier this week thousands of activists marched on central Chicago, where 51 world leaders gathered at the Nato summit.

CND chairman Dave Webb sent a report to members describing the tense and exhilarating atmosphere of the 15,000-strong peace marches.

Protesters were met by a massive security presence and the arrest and injury toll climbed as police sought to prevent their free movement around the city. From inside the maximum-security conference centre, television pictures relayed an enormous circular table to create spurious connotations of democracy.

But the reality is that Nato is a US-led - and largely US-funded - operation.

Despite the accompanying pomp, this conference could hardly be seen as a celebration of Nato success. Behind the veneer was the silent acknowledgement of Nato's impotence and its first big defeat - Afghanistan.

Afghan President Hamid Karzai was, bizarrely, invited to be present, and he was duly photographed amid the Nato heads of government.

A late invitation was also sent to Pakistani President Asif Ali Zardari, who rushed to Chicago but only managed a very brief meeting with Barack Obama where he was barely able to utter his complaints about Nato drones continuing to kill people in villages in north-west Pakistan. Obama and the Nato leaders might live to regret this snub as Pakistan is still refusing to allow Nato supply convoys to cross its border into Afghanistan.

And so 13 blood-saturated years of occupation will draw to a close on December 31 2014, when it is planned that all Nato forces will finally leave Afghanistan and security will be handed over to the US-equipped Afghan army and police force.

In the run-up to 2014 there will be increased contacts with the Taliban, possibly via their office in Qatar - and the Nato leaders blithely swathe themselves in the optimistic view that somehow or other it's all going to be OK.

Of course the Western powers are not really leaving Afghanistan. They intend to maintain a special forces and security presence in the country, and they're well aware that the vast mineral wealth of Afghanistan is waiting to be exploited.

After 10 years of occupation the Afghan people remain as impoverished and wretched as ever, drug production continues to rise and corruption in the civilian administration is rife. And all the while Western taxpayers' money filters through the Afghan political elite to its final destination nestling in secure tax havens all around the world.

Nato was founded immediately after World War II as an instrument of cold war manipulation. Although it initially restricted its activities to the north Atlantic sphere, it has steadily expanded its self-defined "domain."

At no point in its history has it been overly troubled by concepts of democracy or human rights, over the years happily including or collaborating with the governments of ruthless military dictators - witness Portugal, Spain, Greece and Turkey.

Nato's raison d'etre was thwarting the Soviet Union and its allies, not promoting social justice or humanitarianism. The collapse of the Soviet Union in 1990, with the ending of the Warsaw Pact mutual defence strategy, was the obvious time for Nato to have been disbanded.

An era of European security based on co-operation rather than military might could have dawned. Instead, Nato reformed itself, became involved in the Balkans war and has gradually extended its operations so that now it stands atop a pinnacle of global reach.

The European Union's Lisbon Treaty requires massive defence spending by all of its member states. EU members must accept the Nato command structure and co-operate with the body, even though not all - notably Ireland - are Nato members.

Britain was one of Nato's founding nations. The driving forces behind its creation were led by Labour's Ernie Bevin who was foreign secretary in the 1945-51 government. Since then all three major parties in Britain have stuck to their constant refrain of acceptance of Nato membership and its associated invidious encumbrances - US bases on British soil.

The bombing campaign of Libya last year, while not specifically a Nato operation, was made possible by Nato's command structure and surveillance systems. At the end of this pummelling Gadaffi lay dead, Libya's regime had been toppled and a vicious factional conflict had broken out, accompanied by appalling abuses of African workers and migrants. Far from bringing peace and democracy in Libya, Nato has left a legacy of extreme danger.

So now more than ever before, Nato's purpose, costs and operation must be challenged.

Since 1948 this Nato military alliance has gorged itself on resources that could have been so much better deployed on health and poverty-elimination programmes. The ignominious end of Nato activities in Afghanistan provides a golden chance to ask why the world needs such an organisation.

Jeremy Corbyn MP is the national chair of Stop the War Coalition.