Last August, as the Taliban marched into Afghanistan’s capital and displaced the western troops who had spent the previous 20 years protecting it, the German MP Armin Laschet remarked that it was “the biggest debacle that Nato has suffered since its founding”. The total chaos of Nato’s subsequent retreat from Afghanistan sparked a broader debate about whether, in its effort to protect its member states’ interests far beyond their home soil, it had over-reached. As Jean-Loup Samaan, a research fellow at the National University of Singapore’s Middle East Institute, wrote in the journal <i>Insights</i>, the post-Afghanistan moment ought to be one of soul-searching for Nato. A mere six months after Nato’s humbling in Afghanistan, Russia’s invasion of Ukraine brought the threat of war back to the alliance’s very doorstep, and it seemed for a moment that the alliance’s attention was suitably brought back to its founding principle: mutual defence to protect its own members from a direct attack. Nato countries have shored up their own defences, and reinforced one another’s. There is a risk, however, that any step back to basics will be short-lived. On Wednesday, Liz Truss, the UK Foreign Secretary, said that Russia’s campaign in Ukraine, must be a “catalyst for wider change”, in which “Nato must have a global outlook, ready to tackle global threats”. Ms Truss’s comments specifically referenced the Indo-Pacific, where the US’s top military commander in that region argued this week that the alliance could serve as a good model for countries such as Japan, India and Australia. This line of thinking has already provoked ire in China, whose foreign minister Wang Yi warned last month that any effort of that kind would be a ploy “to maintain a US-led system of hegemony”. Such fears may turn out to be overblown. It is hard enough to get Nato countries to work together most of the time; emulating that military co-operation in Asia, where geopolitics is much more complex than in Europe, would be a fraught endeavour. Even so, any signals of renewed mission creep from Nato leaders will raise eyebrows around the world. Two decades ago, a global role for Nato seemed to be the natural course of history for most. When the alliance charged into the US-led global “war on terror”, it enjoyed wide backing, including from allies in the Middle East. In retrospect, that experiment yielded mixed results, at best. The alliance’s hasty and, in many ways unprincipled, retreat from Afghanistan has disillusioned much of the region. Its training mission in Iraq has achieved little. Critics would be right to ask if Nato is really ready for a global role, especially when its allies in Kyiv openly question whether it is able to do enough to protect its neighbours in Europe. Russia’s actions in Ukraine made a certain amount of expansionist thinking in Nato inevitable. By the end of the summer, it is likely the alliance will have two new members in the form of Sweden and Finland. There is, however, an enormous difference between bolstering Nato’s numbers in Europe and taking its fight back out into the rest of the world. When it comes to its core purpose, self-defence, Nato may find, for a second time, that too much ambition can be the enemy of success.