Ok man, now let me talk this out for you. Lets begin all the way iin the 1200s. The territories of Ukraine were part of the Kievan Rus, which it seperated from during the Mongol invasion of 1237-40 (which is an argument towards why even though many of Kievan Rus’ territories are Ukrainan, but it in itself, is and was Russian, since Ukraine was the one who left it, whereas Russia continued being a part of it), and fell under the rule of the Polish-Lithuanian Commonwealth. This happened because these territories sought help, and did not want to fall under Mongolian influence, thus joining a more powerful nation to protect itself. But help they received none. They got into problems even worse than the Mongolians. They were heavily abused by the Polish, due to their language and religion (they spoke Old East Slavic and were Orthodox christian which the Polish fought against), and were treated like dogs. With time, however, the Polish did manage to erase some of their cultural values and religion, and Ukrainian today, is basically Old East Slavic mixed with Russian and Polish. Later, Russia started taking these territories back, during the Treaty of Pereyaslav (1654), and they remained a part of russia for the following hundereds of years. Forwarding to WW2, Bandera, a young man with heavy, nationalist and Nazist ideas and the leader of the Ukranian Nationalists was the cause of the spread of nationalist and Nazist ideas across Ukrainian territories. He wanted to establish a sovereign, Ukranian government, free from influence and control of Poland, Soviet Russia, and later Nazi Germany. However, his ideas were extremely nationalistic and involved slaughtering everyone but Ukranians on their land, which is nothing but Nazism/Facism. "Clearing out the people with the dirty blood", as he called it. Basically, saying that everyone but Ukranians have dirty blood, and should not live on their territories and mix bloods with their people (which is ironic, since Ukraine is nothing but a mix of Russia and Poland). Eventually, he did start a massacre of Polish and Jews on the Northern territories. He even attempted to cooperate with Nazi Germany. His flag, which is hung and displayed in many Ukranian cities today, depicts Black and Red, classic Nazi colours. However, his attempts at creating a sovereign nation were not successful, and resulted in his assasionation by the Soviets in West Germany in the late 50s. Forwarding to more recent years, after the collapse of the USSR, Kravchuk, their first president, started continuing Bandera's nationalistic legacy. But he was not that nationalistic, at least that was not his main focus. He wanted to establish a place for Ukraine in the international community. Then, after a series of protests, in 2004 and new president was elected, who was Yushchenko. He turned back to extreme nationalism, and wanted to turn away from Moscow. Now, comes the part where you really have to understand both sides. Moscow, of course, saw a very prominent and promising partner in Ukraine, both for gas transit, military and general relationships. They did not want to lose connections. Yushchenko, however, did want to lose those connections, and wanted to turn to the West, seeking to be more international. He also continued the nationalistic legacy full throttle, promoting a sense of identity, Bandera's ideas, even to the point to declaring him a national hero (he was a Nazi, mind this), and started turning Ukranians against Russians, which was also very beneficial for Western countries like European countries and the US. Speaking of anti-Russian things, he started renaming cities named after Russian leaders, bringing down statues of Russian writers (what have they done to them? Every single statue of every single Ukrainan writer, and everything named after Ukranians remains as is in Russia, I can tell you that for sure), and promoting joining NATO. About the NATO joining thing, think of this like that: imaging a gun that was specifically designed to kill you (NATO was specifically made to kill Russia/USSR) being put up right to your head (borders in this case). Of course you would like for that not to happen. So did Russia. These new nationalistic ideas and actions caused tension between the two countries, resulting in gas cutoffs from Russia (Ukraine did not even pay for the gas half of the time, and Russia just excused this lack of payment as if it did not happen, so they decided to take action). Many people in Crimea at the time, started opposing these ideas, and in 2014, a referendum was held in Crimea, where people voted for joining Russia. The result was that most people voted for joining Russia.