What is Nato and why was it formed?

World leaders of member states belonging to the North Atlantic Treaty Organisation (Nato) are meeting in Vilnius, Lithuania, on 11-12 July for their latest summit, with Russia’s illegal invasion of Ukraine very much top of the agenda.

Nato is a political and military alliance of North American and European countries forged in the aftermath of the Second World War in the hope of avoiding future bloodshed and hostilities between nations through the realisation of three specific goals: deterring Soviet expansionism, preventing the revival of militant nationalism and encouraging European political integration.

The organisation has its headquarters in Brussels, Belgium, and its current secretary general is Jens Stoltenberg.

Its 31 member states are obliged by Article 5 of the North Atlantic Treaty of 4 April 1949 to come to the aid of any fellow signatory in the event that they should come under attack from a foreign power.

In its own words: “Nato is committed to the peaceful resolution of disputes. If diplomatic efforts fail, it has the military power to undertake crisis-management operations.”

Originally born of the Treaty of Dunkirk signed by Britain and France on 4 March 1947 pledging to contain any future military threat from a revived Germany or the USSR at a time when the Marshall Plan was attempting to bring economic deliverance to a stricken continent still in recovery from a war that had killed 36.5m people, Nato was soon expanded to include Belgium, the Netherlands and Luxembourg and then the US, Canada, Portugal, Italy, Norway, Denmark and Iceland.

Holding firm throughout the Cold War and evolving its approach in response to such tense diplomatic episodes as the Cuban Missile Crisis, the Vietnam War and the USSR’s invasion of Afghanistan, the alliance was given a new lease of life with the fall of the Berlin Wall in 1989, gradually adding former Soviet satellites states to its ranks: first the Czech Republic, Hungary and Poland in 1999 and then Bulgaria, Estonia, Latvia, Lithuania, Romania, Slovakia and Slovenia in 2004.

The most recent additions to the alliance were North Macedonia in 2020 and Finland in 2023.

Sweden, breaking with its long history of neutrality, could be the next to join them in a move that came a step closer to reality in July after Turkish president Recep Tayyip Erdogan signalled he was ready to drop his objections, which included opposition to Sweden’s tolerance of anti-Muslim demonstrations on free speech grounds, support for Kurdish refugees alligned with groups that Ankara considers terrorist organisations and frustration at Turkey’s own exclusion from the European Union.

Hungary is now the only holdout preventing Sweden’s accession and may well fall in line.

Joining Nato gives smaller countries the assurance of military protection by the alliance as a whole, which is why the likes of Bosnia and Herzegovina, Georgia and, most urgently, Ukraine are seeking to join the collective and why Russian president Vladimir Putin is so opposed to the latter two in particular being granted entrance.

Mr Putin has bitterly denounced Nato in the past, falsely alleging that assurances were given to former Kremlin leader Mikhail Gorbachev in the early 1990s that the alliance would not seek to extend its influence east of Germany, only for it to then break that so-called promise first in 1999 and then again in 2004.

“It is obvious that Nato expansion does not have any relation with the modernisation of the alliance itself or with ensuring security in Europe,” he said at the Munich Security Conference in 2007. “On the contrary, it represents a serious provocation that reduces the level of mutual trust.”

The following April, attending a Nato summit in Bucharest at which the alliance pledged future membership for Ukraine and Georgia (without specifying a roadmap and overlooking the reservations of France and Germany), he was even more emphatic: “No Russian leader could stand idly by in the face of steps toward Nato membership for Ukraine. That would be a hostile act toward Russia.”

Four months later, Mr Putin invaded Georgia, destroying the country’s armed forces, occupying two autonomous regions and humiliating a president, Mikheil Saakashvili, who had openly courted Nato membership, actions that brought fresh international condemnation.

Prior to his invasion of Ukraine on 24 February 2022, the Russian president had built up his military forces on the country’s border with its western neighbour, countering international calls for him to stand down his troops with demands that Nato commit to denying Kyiv acceptance into its ranks and that the alliance cease and desist from its activities in eastern member states.

Mr Putin insists that Russia and Ukraine are really one nation and appears to be seeking to reintegrate the country into what he considers to be the motherland, just as he annexed the Crimean Peninsula in 2014.

For its part, Ukraine wants the defensive protection of the alliance as part of its bid for recognition as a free western democracy, shielded from the malign influence of Moscow but US president Joe Biden, an influential voice, has insisted he does not believe it is “ready” to join up.

Without Ukraine being part of Nato, the alliance’s member states, including Britain and the US, are not obliged to commit troops or come to its aid militarily, which is why those states and the other major European powers are reluctant to allow Kyiv into their company for now, as to do so would risk a much more widespread war in Europe.

A number of British troops are, however, currently stationed in fellow signatory states Estonia and Poland as part of the organisation’s peacekeeping duties and the UK has carried out extensive military training with the Ukrainian armed forces since 2015 and has pledged to continue supplying Ukraine with weapons to counter Russian attacks during the present conflict.

Nato’s official position is that membership is open to “any other European state in a position to further the principles of the treaty and to contribute to the security of the North Atlantic area”.

The present concern for the alliance is that, if Russia succeeds in conquering Ukraine, it could continue its westward expansion and perhaps seize other outliers like Georgia and, indeed, set a precedent for other global superpowers to follow, perhaps emboldening China to take Taiwan, for instance.

At present, however, Moscow is a very long way from achieving its goal having been caught unprepared by the sheer ferocity of the fightback mounted by a united Ukraine – well supplied with military hardware by its international allies – rendering its war a drawn-out stalemate that is beginning to look like a monumental miscalculation on Mr Putin’s part that will achieve the direct opposite of his intentions.