The annual NATO summit ended in Madrid on Thursday, and shared a look at how fast Sweden and Finland’s applications to join the military alliance can be and how it can affect soaring tensions between Russia and the West.

“Before the war began, I told Putin that if he invaded Ukraine, NATO would not only be stronger, but also more united,” said President Joe Biden.

For a brief summary, the two Nordic nations were formally invited on Wednesday to join the alliance. German Chancellor Olaf Scholz said they would begin the process of ratifying the planned NATO membership in Sweden and Finland this week and would end it “very soon.”

“We are ready to assure both countries of support now as long as the accession process is not formally completed,” said Scholz.

By comparison, it took more than a year for Northern Macedonia – the latest country to join the bloc – to get through the process.

When the North Atlantic Treaty Organization was formed in 1949, there were 12 members. Today, the number of members has more than doubled to 30 countries.

Every time a country wants to join, the consent must be unanimous among all members, and Turkey had not exactly signed on to Finland and Sweden until Wednesday.

So, what else needs to happen to make it official?

The legislators of all 30 current members must sign an accession protocol before individually ratifying it at home.

Candidates must also formally accept membership obligations. NATO has an “open door” policy in which any country can be invited to join if it expresses an interest, as long as it can and wants to uphold the principles of the bloc’s founding treaty.

The original point of the treaty was to deter the Soviet Union from attacking liberal democracies that lacked military strength. One of the cornerstones of the alliance is Article 5, which states that an attack on one member is considered an attack on all and guarantees that resources from all NATO members can be used to protect each other.

There are some other requirements: NATO members must be democracies, treat minorities fairly and commit themselves to resolving conflicts peacefully.

Nevertheless, this marks a significant shift from two countries that had remained largely unconnected: Finland declared independence from Russia in 1917 and Sweden adopted a neutral foreign policy stance during the Cold War.

– Becoming a member of NATO would actually mean that we leave 200 years of military freedom of alliance, says Swedish Prime Minister Magdalena Andersson. “This was not an easy decision for me as Prime Minister, but I’m sure it was the right decision.”

If Finland joined NATO, it would add another 800 km to the military alliance’s border with Russia. The supplements would also give NATO member countries control over key areas in the Baltic Sea.

Asked about his thoughts on the move, Russian President Vladimir Putin said he had no problem with the two countries joining NATO, but also noted that if infrastructure is distributed to these countries, Russia will respond in a similar way.