The North Atlantic Treaty Organization was created in 1949 by the United States, Canada, and several Western European nations to provide collective security against the Soviet Union this was after world war two.
Nato was originally formed by 12 countries but the number of members has increased to 30 over the years. The growth of members states to NATO is viewed as a threat to Russia and its national interests. According to Articles 4 and 5 of NATO, it states that “An armed attack from either Europe or the USA was to be considered an attack against all the members.”
WHY RUSSIA DOESN'T WANT UKRAINE TO JOIN NATO.
An attempt to join NATO by Ukraine creates a threat to Russia as this will mean Ukraine is taken away from Russias sphere of interest.
History of war between Russia and Ukraine.
NATOs involvement with Russia's war dates back to 2014 when Russia invaded Eastern Ukraine. Putin feels like Ukraine and Belarus were part of Russia after the collapse of the Soviet Union and any process of Ukraine joining NATO should be stopped. Russia's president declared a cease-fire in 2015 following the death of 13,000 civilians. However, his cease-fire came with a number of demands that Ukraine totally disagreed with. Russia demanded that Ukraine should not be allowed to join NATO as it expanded to Eastern Europe.
Following the invasion, NATO responded by suspending its cooperation with Russia and boosting the defense of Ukraine's capital Kyiv. They did this by holding military training but not taking part in the war process. Russia's recent invasion of Ukraine was as a result of USA sanctions against Russia. Although little is currently been done to help Ukraine as it's not a member of NATO, Nato troops have been sent to countries that border Russia.