Finland to officially join NATO on Tuesday

Finland is slated to become NATO's 31st member on Tuesday after Turkey ratified the Nordic country's application to the world's largest military alliance. 

"It will be a good day for Finland’s security, for Nordic security and for NATO as a whole," NATO Secretary General Jens Stoltenberg said Monday.

All members of the alliance must approve new members, and Turkey had been opposed to Finland's membership. 

Sweden had jointly applied to join NATO with its neighbor Finland last year, but Turkey is still opposed to Sweden's bid to join the alliance. Turkish officials have accused Sweden of not being aggressive enough to battle groups it deems to be terrorists.

By joining NATO, Finland, which shares a more than 800-mile border with Russia, will more than double the size of the alliance's border with Russia. 

The Kremlin previously threatened to position nuclear weapons in the Baltic Sea region and deploy naval forces off Finland's coast if the country joined NATO.