It was born in the Cold War, did not see action on a battlefield until 46 years later and is now fighting far afield from its European home base against enemies as diverse as the Afghan Taliban and seagoing pirates in the Horn of Africa.
The North Atlantic Treaty Organization, at 61, is an old soldier in a new world - a lot beefier than in its salad days, somewhat unsure of its marching orders and battle-bruised. The clarity of purpose it had when the Soviet Union was defined as the single biggest threat to European-American security has since been muddied, and instead it finds itself bogged down in a war far from its historic theatre of operations.
The two-day summit ending Saturday in Lisbon is a chance for leaders of the 28 member countries to say where they are headed. They are speaking of big ambitions for the alliance as both a political and military force: overseeing an integrated missile defence shield, shifting resources to develop a cyberwarfare strategy, embarking on a new dialogue with Russia, intervening to pick up the pieces in failed states, engaging with China, even mediating between intractable rivals such as Pakistan and India.
But as they chart out the future, their more immediate worry is how to unwind the decisions of the past.
The alliance "stumbled," rudderless, into a prolonged war in Afghanistan, according to a Rand Corporation study published this week, and will be indelibly marked by its outcome.
"A successful mission in Afghanistan could promote the vision of NATO as a global security alliance capable of undertaking a wide scope of operations, ranging from diplomatic engagement to peacekeeping operations and even to combat operations beyond the bounds of the treaty area," the report said. Anything less will probably make it gun-shy of a global role for years to come.
At the summit, NATO leaders will set 2014 as the target date for disengaging their troops from combat in Afghanistan. Canada's soldiers leave next summer, but acceded this week to a request from the organization to leave military trainers there for the duration of the NATO operation to prepare Afghan soldiers and police.
The summit also adopted an updated "strategic concept," outlining the alliance's purpose and fundamental security tasks. It was the first rewrite in 11 years.
The threats it describes are far different from the one envisioned when NATO was created: a hostile army at the gates of Europe. The new threats include rogue states with ballistic missiles, pirates who disrupt international shipping and cyberterrorism that could bring the world financial system or power grids crashing to a halt.
Yet in significant ways the new assessment is a catch-up document. Its explicit subtheme is that the threats and required responses may take NATO far beyond the actual borders of its members. In other words, it may have to do what it has already done in Afghanistan.
"NATO's core function is still territorial defence of our populations and our member states," Secretary-General Anders Fogh Rasmussen said this week. "However, we have to realize that in today's security environment it may on occasion be necessary to go beyond our borders to protect our people effectively. Afghanistan is a case in point."
Afghanistan is also a cautionary tale of the risks of ambitions, and of straying too far from the core purpose of collective self-defence that lies at the heart of the transatlantic alliance.
The NATO expedition in Afghanistan began in the wake of Sept. 11, 2001, as a retaliatory attack on the Taliban regime that was hosting al-Qaeda. It was the first time in the history of the alliance that its members invoked the founding doctrine that an attack on one, in this case the United States, is an attack on all.
With American forces preoccupied with Iraq, NATO expanded its reach in Afghanistan but without a concomitant investment of manpower and planning. From the narrow focus on overthrowing the Taliban and chasing out al-Qaeda, the mission evolved into a more amorphous one of pacification and reconstruction of a nation. In retrospect, that was unfortunate hubris.
"Much of what NATO decided to do vis-à-vis Afghanistan was driven by this need to find a new purpose for NATO," said François Heisbourg, a defence expert at the International Institute for Strategic Studies, in Paris. "It was a big show," he added, "so you had to assign it big objectives, and that was the basic mistake."
As NATO looks ahead, its ambitions will also be curtailed by the financial crisis that has hit hard on both sides of the Atlantic. The bureaucracy is set to shrink. Mr. Rasmussen, the former Danish prime minister who has been secretary-general since August, 2009, has proposed trimming the headquarters staff by about 30 per cent to "cut fat and build muscle."
In many European countries, financial constraints have led to trimmed domestic defence budgets and may also dampen the appetite for new spending projects.
The grumbles within the alliance over resources and the long process of negotiation required to reach consensus have been a permanent fixture of alliance forums and debates. "You have to remember," said a French diplomat in Paris, "that NATO is 98-per-cent boredom and 2-per-cent hysteria."
Successive American administrations have complained that European governments do not contribute enough, and the Obama administration has made the same complaint. The Europeans complain about American heavy-handedness.
Disagreements over whether the future security strategy should include a nuclear deterrent divide France, with its nuclear arsenal, and many in the German government who see the missile-defence idea as a potential substitute. Former Soviet bloc states want NATO to refocus on its core defence mission in Europe against possible Russian aggression.
As the Lisbon summit demonstrates, the goal of NATO leaders now is to get out of Afghanistan without leaving the country less stable and just as dangerous to Western interests as it was when the alliance went in. The experience may make the alliance more cautious about expeditions in far-away places, but it is unlikely and probably impossible for it to retrench too far back into its Cold War Europe-centric focus.
In an interview with The Financial Times, German Foreign Minister Guido Westerwelle said NATO has more than a military or defence role to play. "It is clear that NATO sees itself as a political union of values," he said.
Mr. Rasmussen has also suggested that the Afghanistan experience opens up new possibilities that give the alliance a new purpose - as an intermediary to ease the long-standing and seemingly intractable rivalry between India and Pakistan.
Stability in Afghanistan requires "positive engagement from Pakistan," he said this week. "We also have to ease tensions between Pakistan and India. So we should also engage with India. And we know that China can play an instrumental role in stabilizing the whole region."
These are grand ambitions that may prove too much to digest for NATO members that are now focused on disentangling themselves from Afghanistan. "NATO is still working its way through the changes that have occurred in the world since it was created," a German diplomat said. "It is a process, and the process is continual and ongoing."
Globe and Mail reporter Susan Sachs has been a New York Times bureau chief in Cairo, Istanbul and Baghdad. She was a Pulitzer Prize finalist while at the Miami Herald.