EXPLAINED: How would it affect Sweden if Finland joined Nato alone?

When did Sweden develop its military cooperation with Finland? 

It really took off following Russia's annexation of Crimea in 2014. "We decided that we should have our most intimate defence cooperation with Finland," Westberg says. "Since we are both non-aligned, we could even do collective defence planning to fight a war, and we have since then coordinated on legislation so that we can operate from each other's territory, and we have built up a common marine battle group." 

In 2014, Sweden and Finland signed an action plan to deepen defence cooperation, and then in 2015, the Swedish government gave the Armed Forces a mandate to develop a more extensive defence partnership with Finland. The Swedish Armed Forces details the main areas of cooperation here on its website. 

In 2018, the two countries signed a Memorandum of Understanding, which gave each country's armed forces access to the other country's territory, gives mutual 'host nation' support, and also laid out how the two countries would run joint exercises and training, share surveillance, and develop measures to enable "joint military action, including operational and tactical planning and interoperability". 

Jacob Westberg, right, is an associate professor at the Swedish Defence University. Photo: Anders G Warne.

"If we look at the Finnish and Swedish defences, the differences between the countries make them mutually complementary," Westberg tells The Local.

Finland's system of universal male conscription means it can mobilise 280,000 trained soldiers, he adds, pointing out that this is "an asset that Sweden does not have", and is "quite a large army in the modern European context".

Finland also has the largest artillery in western Europe, with an advanced missile defence system which can reach targets far inside Russia. 

Sharing surveillance with Finland also gives Sweden much better visibility over both the eastern Baltic and over the Arctic North. "We get the benefits of earlier warnings, as we have access to Finnish radar," Westberg says. 

The two countries' air forces have trained extensively together and established infrastructure that means that their respective planes can operate from each other's airbases. "That is a great advantage for Finland, for instance, as they could defend Finland from Swedish soil," Westberg notes.

Since 2014, the two countries have developed a joint marine force that combines different units from the Finnish and Swedish sides, and which, according to Westberg is "now considered operational as a battle group". 

Do Finland and Sweden have a commitment to come to one another's aid if one is attacked? 

No. While the governments of Finland and Sweden in 2015 instructed their armed forces to develop common defence planning, this was never backed by a mutual defence clause. 

"What they didn't do was to seal this deal with mutually binding defence commitments," Westberg notes. "I have long said that this is a problem because it affects the credibility of this cooperation." 

The two countries' history makes this trust issue particularly acute. In November 1939, Sweden pointedly did not come to Finland's aid when it was invaded by the Soviet Union, despite the detailed plans the two countries had drawn up for joint defence. 

"Of course, the Finns remember this, so they have been much more active before the present war in arguing for a defence alliance with Sweden, but Stockholm hasn't been very keen," Westberg says.  

So what will happen to the defence cooperation if Finland joins Nato and Sweden doesn't? 

Finland would not even be allowed to come to Sweden's aid unless it won the approval of the other Nato states. 

"If Finland joins Nato, they will not be able to come to Sweden's help if Nato isn't already involved in the conflict, so that part of Sweden's defence cooperation would have to go," Westberg says.

"We know this since Denmark and Norway have consistently told us that when it comes to collective defence, we have to give priority to Nato, because it is a defensive alliance, so we cannot come to your help if Nato is not involved." 

Finland joining Nato would also make Sweden more vulnerable by changing the power dynamics in the Baltic Sea. Sweden might come under greater pressure from Russia as the last non-aligned state in the Baltic Sea area. 

"There are reasons to assume that Russia would then have an even greater interest that we then remain so, because otherwise the Baltic Sea would be a totally Nato area except for Kaliningrad and the inner part of the Gulf of Finland," Westberg explains. "So the pressure on Sweden to remain neutral might increase."  

Finally, if Finland joined Nato it might increase the risk that Russia invades the Baltic island of Gotland, as part of an attempt to reassert dominance over one or more of the Baltic states. 

"Russia has very strong reasons to either demand that Sweden closes its territory for Nato troops, so that they can't reinforce the Baltics from Swedish territory, or they may even establish control over some parts of Swedish territory to install air defence systems and anti-ship missiles so that they will be able to deny Nato access to a greater part of the central and southern Baltic Sea." 

But Sweden cooperates with Nato today, so why couldn't it cooperate with a Nato Finland? 

The crucial period is the immediate period after an attack, before any of Sweden's Nato allies have been able to decide whether or not to come to Sweden's defence. 

"During the first the first, let's say, 48 hours of conflict, you're depending on resources that are available in the area and Finland and Sweden have those resources when it comes to supporting each other," Westberg said.

Losing its partner in this early 48-hour period would weaken Sweden's defences significantly. 

"Norway may also have some resources, but they won't be able to give them to us until Nato is under attack and they move into conflict, so it would be a considerable loss if we would no longer be able to plan for the common use of resources with the Finns".