Now all NATO members must decide to start ratification processes to allow Sweden and Finland into NATO.
In the next few days, the NATO countries are expected to make a decision to invite Sweden and Finland and create membership negotiations.
When NATO then concludes membership negotiations, Sweden will become an "invited member".
What is the difference between being an invited member and not a full member?
- When you are invited, you are allowed to attend all meetings, but you are not allowed to vote.
What you want in a membership is above all NATO's defense guarantees, and you are not covered by them before you are approved by all countries.
It is often said that one is therefore more vulnerable to external threats during this time, says Eva Frisell, research leader at FOI's unit for security policy.
The Russian invasion of Ukraine contributes to an increased urgency to approve new members quickly for many of the member states.
It is also of the utmost importance to NATO;
and in particular the Baltic countries;
to show a strong and united front.
Therefore, a faster membership process is expected for both Sweden and Finland.
Many have talked about speeding up the membership process for Sweden and Finland. How long is it reasonable for Sweden and Finland to become full members?
- The ratification process depends a bit on what the legislative periods look like in the other countries.
Previously, it took between eleven and fourteen months.
Many NATO countries have already prepared for this process in view of the current security situation.
A year is a reasonable time to think, but should a new election or the like take place in a NATO country, it may prolong the process.
See the expert Eva Frisell describe Sweden's three biggest challenges above.
First NATO meeting
The letter with the application is processed by the NATO countries during the meeting in Madrid.
The talks, led by one of NATO's eight assistant generals, are only expected to take a single day.
Decisions to invite Sweden and Finland to NATO are expected to be made during the meeting, according to Secretary General Jens Stoltenberg.
NATO produces a report establishing whether Sweden and Finland live up to the requirements.
Each country replies that they understand what applies and still want to move on.
Invited member
Today, the leaders of the NATO countries welcome Sweden and Finland into the defense alliance.
The formal decision to invite the countries is expected to be taken by the NATO countries' ambassadors in Brussels on Tuesday.
In that case, an additional protocol to the NATO Treaty will also be sent out for ratification by the parliaments of the NATO countries.
The NATO countries make a joint decision on whether it is possible to sign the accession protocol.
NATO has previously said that these steps can be completed in a total of two weeks.
However, several countries, such as Denmark and Estonia, have already given their initial green light.
When the minutes are signed, Sweden becomes an "invited member" or "invitee" with the right to participate in all NATO meetings, but without the right to vote.
Approval
The minutes are then sent to the 30 Member States for final approval in each country's parliament.
It normally takes at least six months, but is expected to go faster now.
NATO Secretary General Jens Stoltenberg expects it to go "fairly quickly, as allies are ready to do so as soon as possible".
NATO member
When all countries have done their thing and the applicant country has signed and all the paperwork has been filed in Washington, you become a full member.
It can take up to a year before Sweden becomes a full member.
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What is happening now for Sweden in the NATO process?
Andreas Öbrink, SVT's reporter on site in Madrid explains.
Photo: Filip Huygens / SVT and Stephanie Lecocq / EPA / TT