STOCKHOLM, (Reuters) – The Russian invasion of Ukraine has pushed Finland to apply for NATO membership.

Finland and Sweden share a border of 1,300 km (810 miles) with Russia. Moscow warned that they could use nuclear weapons or hypersonic missiles to attack the European exclave at Kaliningrad.

The wait will be long for any applications to NATO, which could cause tensions in all NATO member nations. But the White House has stated they believe that security concerns can be dealt with in the interim.

These are the key issues leading to radical changes in policy. What next steps can be taken towards joining the U.S.-led 30-nation alliance?

WHY ARE SWEDEN and FINLAND NOT NATO MEMBERS

Despite the fact that they have relatively few military forces, Russia and both countries are non-aligned.

Finland was granted independence by Russia in 1917. It fought two wars against Russia during World War Two, during which it lost territory to Moscow. In 1948, Finland signed the Agreement of Friendship, Cooperation and Mutual Assistance with Russia. This established a level of political and economic dependency and isolated it from Western Europe militarily.

As the threat of Moscow diminished, the end of Cold War brought about a disintegration of Soviet Union.

To maintain peace, it has relied upon its military deterrence as well as friendly relations with Moscow. Russian President Vladimir Putin is anything but friendly when it comes to Russia’s invading Ukraine. Moscow refers to this as a “special operation”.

Sweden has not been involved in a conflict for over 200 years. After the war, its foreign policy was focused on international democracy and multilateral dialogue.

After the Cold War ended, it reduced its army in hopes that in any future conflict it would be able to delay the Russian advance and wait for help. Putin’s aggression against Ukraine makes a promise of assistance much more appealing.

But, there are many leftists in Sweden that remain skeptical about the U.S. security agenda. NATO is based on deterrence from the U.S. arsenal.

Since 1995, Sweden and Finland have switched from being neutral to military alignment.

In response to Russia’s growing belligerence, both countries have become closer to NATO over the years. They exchange intelligence and participate in exercises as part of their alliance.

By joining the alliance, Sweden and Finland would be covered by Article 5. This guarantees that any attack against one NATO ally will result in an attack upon all.

WHAT IS THE SUPPORT FOR NATO MEMBERSHIP?

According to polls, a significant majority of Swedes are in favour of joining NATO. Support is just below 60% as per the most recent poll. A majority of parliament members support an application.

The largest party in Sweden, the Social Democrats (the most powerful and the one that has ruled for the past century), have long supported military non-alignment. However they are currently reviewing their objections. A decision about whether or not to join the Union is expected on Sunday. It is widely believed that they will support membership.

– Although the Swedish Left Party (formerly communist) is against joining, so does the Green Party. However, if the Social Democrats changed their stance, it would result in an overwhelming majority of parliament for membership.

According to opinion polls, Finland is more popular than Sweden in support of membership. Many Finns are aware of Russia’s long border and support a Finnish application.

This week, the Finnish defence committee stated that NATO membership was the best way for Finland to ensure its national security.

Finland’s President Sauli Niinisto, who is likely to make a statement on Thursday about his views on NATO joining, is seen with Prime Minister Sanna Marian also making her comments. It is widely believed that both will support the application.

WHERE COULD THEY JOURN?

Finland is a NATO member. This option allows for the application of specific actions if the security situation becomes more dire. The Swedish Parliament will also present a review of security policy on Friday. However, it’s not likely to include any recommendations about NATO.

Sweden’s Social Democrats called for a Monday parliamentary discussion on NATO. If the party is expected to return, the government can call Riksdag votes about sending in an application. However, it’s not required by law.

The Social Democrat Prime Minster Sanna Martin, Finland’s Five-Party Centre-Left Coalition leader, has been visiting different NATO members countries over the past weeks to gain support for an application.

– Magdalena Andersson is a Social Democrat and the Swedish Prime Minister. She has held many other meetings with NATO leaders, as well as with Boris Johnson, the British Ambassador to Sweden, while on Wednesday’s tour of Finland and Sweden.

There is no deadline for applying, but here are the steps to NATO membership that apply for Helsinki/Stockholm.