20 years ago, as part of a series of events connected with NATO’s 50th anniversary, Prime Minister Tony Blair gave a speech in Chicago entitled “The Doctrine of the International Community”. I had been asked to provide some ideas for the speech a couple of weeks before it was due to be delivered. Somewhat to my surprise, these ideas appeared with only limited amendment in the final version of the speech.

The speech was interpreted at the time in the light of what was going on in Kosovo, where the NATO campaign had reached a difficult stage and some hard decisions were being taken about whether to use ground forces to supplement air strikes. It was interpreted later in terms of what happened with Iraq, although, contrary to what has since been claimed, the speech specifically rejected regime change.

What it did do was offer five tests against which any proposed intervention should be judged: being sure of the case, exhausting diplomacy, military feasible options, being ready for the long term, and acting in line with national interests. At least in my mind these were supposed to be restrictive rather than permissive, but of course it was how the Prime Minister understood it that really mattered. (I have discussed elsewhere what I wanted to do with the speech.)

The timing was significant. The enlargement of NATO had begun, taking in countries that had recently been part of the Warsaw Pact. The Czech Republic, Hungary and Poland had only recently joined when the Kosovo War began. The alliance had already been heavily involved in Bosnia, but Kosovo was different. Kosovo was a province of Serbia, and in seeking to protect the population from persecution and expulsion, the alliance was directly interfering in Serbia’s internal affairs. This reflected an important shift in thinking since the end of the Cold War. As we now know, the Russian Federation, whose sympathies lay with the Serbs, viewed this development with foreboding. It is this moment to which Vladimir Putin regularly refers when explaining the harsh turn in his country’s relations with NATO.

This was the start of a longer-term deterioration in NATO-Russian relations which had ups and downs thereafter. Putin’s major anxieties revolved around the West’s support for the colour revolutions in Georgia and Ukraine as attempts to impose Western norms and alliances on neighbouring countries. But these reflected a conviction that the West would try to topple regimes it did not like (including his). Blair’s Chicago speech noted that the UN Security Council was not working as it should (and it ducked the issue of legal test) and expressed the hope that this would change. But the assumption at the time was that cooperation with Russia would still be possible.

Kosovo was also important in demonstrating, in ways that would have been unthinkable just a decade earlier, that NATO could organise and give political direction to an intervention force. The process had begun with Desert Storm, to liberate Kuwait from Iraq, in 1991. But this was an operation under UN sponsorship and not NATO’s. The post-war support for safe havens for the Kurds was more direct intervention in Iraqi internal affairs but this did not involve any actual fighting. Over the 1990s the idea that Western countries would get involved in trying to sort out distressing situations in unstable parts of the world took hold. Kosovo was the conclusion of that trend, justified by reference to humanitarian imperatives.

That meant that at the time of the terrorist attacks on the US of 11 September 2001 an interventionist mindset was in place. NATO countries were all involved in some way in the subsequent effort to overthrow the Taliban regime in Afghanistan in 2001, and in 2003 responsibility for the International Security Assistance force was passed to the alliance. There was no comparable unity with Iraq, where opinion was much more divided. Even Blair acknowledged in his memoir that applying the Chicago tests would not have given the operation a straightforward green light.

The failures in Iraq – both in terms of finding weapons of mass destruction and stabilising the country once the regime had been toppled and terrible violence unleashed – undermined enthusiasm for intervention. With Libya, in 2011 the response was confined to air power, which meant that once Gaddafi was overthrown there were no forces on the ground capable of keeping the situation calm. With Syria, first Britain and then the United States veered away from military action after making initial preparations to respond to the use of chemical weapons. Their later efforts were specifically directed against ISIS and had a security as much as a humanitarian rationale.

The moment represented by Chicago has thus passed. It was a time when Western governments were optimistic about their own prospects and ambitious about their international roles. They enjoyed considerable freedom of manoeuvre, with supportive publics and few external restraints. My draft for the speech was an attempt to answer the criticism that in these conditions and without the old norm of non-interference Western countries would have carte blanche to meddle in local matters that had little do with them.

It was an attempt to inject some caution, but it obviously assumed that more interventions were possible. Otherwise the tests would not have been necessary. Should the mood return, the tests would still be helpful. For now, Western countries have lost their swagger. Not only are they more aware of the pitfalls of intervention, but more traditional threats, notably Russia’s attempts to coerce its neighbours and destabilise the rest of Europe, have led to its refocusing on the sort of larger-scale security threats for which NATO was first designed and to which it may be most suited.

Professor Sir Lawrence Freedman is Emeritus Professor of War Studies, King's College London.