Russian military intervention in Scandinavia and the Baltic

The Russian military intervention in Scandinavia and the Baltic, sometimes called the Northern European War was a series of operations carried out by the Russian military and the Russian Special Operations Forces between 1 September 2015 until 25 December 2016, when a treaty was signed to end all hostilities that took place inside Europe.

The intervention started with the siege of Rovaniemi, which was a series of attacks carried out by the Russian 6th Army, supported by the 1st Guards Tank Army. Despite failure to capture the city, the Russian military still advanced into Lapland, until they were caught by the Finnish military, reinforced by Swedish military and Estonian military, near the city of Sodankylä. The Russian military suffered extremely heavy casualties during the battle, despite heavily outnumbering the Finnish and Estonian military four-to-one. The Russians were forced to surrender on 25 September 2015.

Finland saw the opportunity and captured the remaining Russian personnel, demanding a ransom from the Russian government. The ransom stated that the prisoners will be released if the Russian government will sign a treaty to end hostilities, as well as giving Finland the territories of Karelia and Murmansk, two Russian federal subjects which were heavily influenced by the Finnish culture and language. The Russian government rejected the ransom, and began smaller skirmishes inside Lapland. The prisoners of war were eventually forced to turn their allegiance into the Finnish military. On 30 September 2015, the Finnish military began their advancement into Russia, with the aim being to capture Karelia, Murmansk and Saint Petersburg. Initial advancement was rather weak, but on 19 October 2015, the Finnish military captured the city of Murmansk and on 8 November 2015 they captured Petrozavodsk, the capital city of Karelia. On 12 November 2015, the Finnish military began the siege of Saint Petersburg, which lasted until 6 December 2016. Despite being slightly outnumbered, the Finnish military captured the city, soon after proclaiming it as the capital city of Finland. Despite the proclamation, the status of Saint Petersburg becoming the capital city of Finland did not go into effect until 6 December 2020, on the four-year anniversary on the end of the war. The city had to undergo several repairs, but according to the Finnish government, it was "completely repaired" on 7 May 2020.

The war also took place in the Baltic, mostly inside Estonia and Latvia, both of which had different allegiances. Despite both being members of the European Union and NATO, they were temporarily suspended following several skirmishes on the border of the two countries. On 8 September 2015, following Latvia declaring an alliance with Russia, the Latvian military began operations near the border-city of Valga. The Estonian government responded by forming a military alliance with Finland and a economical-political pact with Sweden and began operations near the border-city of Valka in Latvia, a city that was twinned with Valga.

The Estonian military continued their advancement into Latvia by attacking several "military zones" inside Latvia, with the Latvian military inside Estonia unable to continue operations due to a lack of telecommunication with the Latvian government. The Estonian military began naval invasions of Latvia by invading the Gulf of Riga, but were unsuccessful in their operations.

On 9 August 2016, a peace agreement was signed between the Estonia and Latvia, which saw them break their alliances with Finland and Russia, respectively. No territorial changes were made, but several mild skirmishes continued between Estonian and Latvian terrorist groups.

Military strength
Albeit military strength is disputed during the war, there are some documents that seem to describe the exact size of the armies who fought in the war.

GENERAL MILITARY SIZE:
Finland:

Russia:

Estonia:

Latvia:

Sweden:

Military and civilian casualties
According to a number of different reports, a total of 6,654,315 casualties, both military and civilian have been reported.

Territorial changes inside Finland, Estonia and Russia
An indirect Finnish victory over Russia was declared on 24 December 2016, a day before the Finland, Estonia and Russia signed an official non-aggression pact that ended hostilities but equally allowed Karelia and Murmansk Oblast to enter Finland as "unofficial autonomous states". Due to foreign pressure, the Finnish government and Russian government agreed to this treaty, which officially ended the war. A part of the agreement also claimed that the Leningrad Oblast, which housed the economically-politically important Russian city of Saint Petersburg, was to become an autonomous region inside Finland with high levels of autonomy and would still serve as an "indirect autonomous federal subject" of Russia.