What is Nato, which countries are members and why has Sweden joined?

Since Russia's invasion of Ukraine, Nato has admitted Sweden and Finland as new members and has also been bolstering its defences in eastern Europe.

What is Nato and when was it set up?

Nato - the North Atlantic Treaty Organization - was formed in 1949 by 12 countries, including the US, UK, Canada and France.

Its aim was to block expansion by the Soviet Union - a group of communist states which included Russia.

Members agree that if one of them is attacked, the others should help it defend itself.

Nato does not have an army of its own, but member countries can take collective military action in response to crises. They also coordinate military plans and carry out joint military exercises.

After Russia's invasion of Ukraine in February 2022, Nato said that it posed the "most significant and direct threat to allies' security".

Which countries are Nato members?

Nato now has 32 members across Europe and North America, including the UK, US, Canada, France, Germany, Italy, Spain and Turkey.

After the Soviet Union's collapse in 1991, many Eastern European countries joined: Albania, Bulgaria, Hungary, Poland, the Czech Republic, Slovakia, Romania, Lithuania, Latvia and Estonia.

Nato members states, including recent joiners Sweden and Finland (March 2024)

Sweden and Finland applied to join in May 2022, following Russia's invasion of Ukraine. They had been neutral for decades.

Finland - which has a 1,340km (832 mile) land border with Russia - joined in April 2023.

Sweden became a member in March 2024, after its membership was held up by both Turkey and Hungary.

Turkey said Sweden had been giving refuge to members of groups such as the Kurdistan Workers' Party, which it considers a terrorist organisation. However, it decided to back Sweden's membership in January.

Hungary's government was angry that Sweden had accused it of behaving undemocratically, but agreed to let it join in February.

With Sweden and Finland joining Nato, it is seeing its biggest expansion since the 1990s. They will add nearly 300,000 active and reserve troops to the alliance's ranks.

Ukraine, Bosnia and Herzegovina, and Georgia also hope to join Nato.

How Sweden and Finland went from neutral to Nato

When will Ukraine join Nato?

Nato's secretary general, Jens Stoltenberg, has said it is "inevitable" that Ukraine will become a member, but not until its war with Russia ends.

President Zelensky has asked for Ukraine to be admitted as soon as possible afterwards.

Since July 2023, the Nato-Ukraine Council has coordinated efforts to help Ukraine defend itself against Russia.

Russia has consistently opposed the idea of Ukraine joining Nato, fearing it would bring the alliance's forces too close to its own territory.

Nato asks member states to spend at least 2% of their national income on defence.

The US spends nearly 3.5% and several countries which border Russia - such as Poland and the Baltic Republics - also spend more than 2% on their armed forces.

UK spending is just above the 2% target.

However, countries such as France, Germany, Italy and Spain spent less than the target in 2023.

Former US President Donald Trump, who is campaigning for re-election, controversially said he would encourage Russia to attack Nato countries which failed to spend enough on defence.

Nato said there was an "unprecedented rise" in defence spending by several members in 2023, and that 18 countries were expected to meet the 2% level in 2024.

What weapons are Nato countries giving Ukraine?

As a group, Nato has not sent weapons to Ukraine, but several individual member countries have.

The US, UK, Germany and Turkey have provided anti-tank weapons, missile defence systems, artillery guns, tanks and military drones.

The US is allowing two Nato countries, Denmark and the Netherlands, to transfer US-made F-16 fighter jets to Ukraine, once pilots have been trained to fly them.

Ukrainian media say the first planes could arrive in spring 2024.

However, Nato countries have not sent troops to Ukraine, and ruled out using their air forces to impose a no-fly zone over the country, because of fears such action could provoke a direct conflict with Russia.

In 2023, Nato commanders agreed detailed plans for countering possible Russian attacks in the Arctic and north Atlantic, central Europe, or the Mediterranean region.

It also announced plans to increase the number of its troops in Europe on high alert from 40,000 to more than 300,000. In addition, it has bolstered its defences on its eastern flank, bordering Russia, with eight battlegroups.

Until the end of May, Nato is staging Steadfast Defender, one of its largest ever military exercises, involving 90,000 personnel from all Nato countries - including Sweden.

-bbc