Russian aggression prompts NATO expansion

 ISW:

...

The Kremlin intensified its information operation accusing NATO expansion of presenting a military threat to Russia.[1] Shoigu stated that NATO’s military expansion near Russian borders, including Finland’s and Sweden’s NATO membership aspirations, necessitates an "appropriate" Russian response to establish a Russian force group in northwestern Russia.[2] Senior Kremlin officials said that the accession of the Nordic states to NATO would not threaten Russia in spring 2022. Kremlin Spokesman Dmitry Peskov stated that Finland and Sweden joining NATO would not present an existential threat to Russia in April 2022 and Russian Foreign Minister Sergei Lavrov stated that Finland and Sweden joining NATO would not make "much difference" in May 2022.[3]

Shoigu publicly presented a series of proposed Russian defense policy changes to significantly increase the size of the Russian military. Shoigu proposed that Russia reestablish the Moscow and Leningrad military districts, form a new army corps, and form 17 new maneuver divisions.[4] Shoigu suggested that Russia form a new army corps in Karelia, two new airborne assault divisions, three new motorized rifle divisions in occupied Kherson and Zaporizhia oblasts, and expand seven existing brigades of the Northern Fleet and Western, Central, and Eastern Military districts into seven new motorized rifle divisions while expanding five existing naval infantry brigades into five naval infantry divisions. Shoigu also proposed that Russia form five artillery divisions to support military districts.[5] He proposed increasing the strength of the Russian Armed Forces to 1.5 million servicemen, including 695,000 contract servicemen (Shoigu said in spring 2021 that 380,000 Russians were contract servicemen), gradually increasing the age of conscription for military service from 18 to 21 years and raising the age limit for conscripts from 27 to 30 years. Shoigu did not specify a timeline for these measures.

This is not the first time the Russian MoD has signaled its intention to reverse the 2008 Serdyukov reforms that largely disbanded Russian ground forces divisions in favor of independent brigades. The Russian MoD has been steadily reversing the Serdyukov reforms by restoring maneuver divisions across Russian military districts since 2013.[6]

...

First.  NATO has never started a war with Russia or any other major power.  It is primarily a defensive organization to defend against aggression from countries like Russia.  When Putin invades another country under the false pretense of "fighting Nazification" and with the intention of annexing it into the Russian Federation, it should not be too surprising that other neighboring countries to Russia would want the defensive support of NATO to forestall other aggression by Russia.