Why did Russia attack Ukraine?

It's been five days since Russia invaded Ukraine, fighting has since been going on between soldiers of both countries. Major landmarks in major cities of Ukraine have been taken down, civilian structures destroyed and some civilians killed. The question most people seek to ask is; What actually called for this war? 

The North Atlantic Threaty Organization, NATO, was formed after the second world war by the United States , Canada,  England, Germany, France and some other European countries just to mention a few. Their main aim was to unite and stop a Soviet Union which kept on growing and gaining more power in Asia and some parts of Europe. This made it clear that NATO members were outright enemies of the Soviet Union and vice versa. 

Fast forward in April 1961 when the Nazis have already surrended after WWII, the United States invaded Cuba, a sovereign country. Their reason was that Cuba, their neighbour had formed a Communist Government which makes them align to the Soviet Union and for that matter posses a serious threat to the United States. The main aim of the invasion was to topple the then Communist Government and install a government that will be in alignment with the United States. This happened as the whole world observed. 

In December 1991, the Soviet Union was disintegrated allowing member states to form independent countries on their own hence forming present day Russia. According to Vladimir Putin who then was not the president of Russia described this move as "the greatest catastrophe of the 21st century" . In 2014, a Vladimir Putin lead Russia invaded Crimea an isolated portion of Ukraine, Russia's next door neighbour and facilitated a war between Ukraine separatist regions of Luhansk and Danask following Ukraines intension to join NATO, Russia's greatest enemy.

Now in 2022, Ukraine, more than ever is very close to joining  NATO. Russia who shares border with Ukraine and also shares a lot in common as well as a similar historical background with the Ukranian people feels it's security is threatened by the move made by Ukraine to join NATO. President Vladimir Putin sees no other way to avert this decision by Ukraine other than letting history repeat itself by invading Ukraine.

Now it's five days into the invasion of Ukraine by Russia, military men and civilians have been killed, some structures destroyed, Russia takes control of certain parts of Ukraine, NATO sends in weapons to the Ukranian army, countless sanctions on Russia from all angles, Putin puts nuclear deterrents on high alert, contingents from both sides meet at the Belarusian border to negotiate cease fire terms. Now guess what, war CONTINOUS ...

This in a nutshell is why Russia is at war with Ukraine.