This all began as an internal Ukrainian crisis in November 2013, when President Viktor Yanukovych rejected a deal for greater integration with the European Union (here's why this was such a big deal), sparking mass protests, which Yanukovych attempted to put down violently. Russia backed Yanukovych in the crisis, while the US and Europe supported the protesters.

Since then, several big things have happened. In February, anti-government protests toppled the government and ran Yanukovych out of the country. Russia, trying to salvage its lost influence in Ukraine, invaded and annexed Crimea the next month. In April, pro-Russia separatist rebels began seizing territory in eastern Ukraine. The rebels shot down Malaysian Airlines flight 17 on July 17, killing 298 people, probably accidentally. Fighting between the rebels and the Ukrainian military intensified, the rebels started losing, and, in August, the Russian army overtly invaded eastern Ukraine to support the rebels. This has all brought the relationship between Russia and the West to its lowest point since the Cold War. Sanctions are pushing the Russian economy to the brink of recession, and more than 2,500 Ukrainians have been killed.

A lot of this comes down to Ukraine's centuries-long history of Russian domination. The country has been divided more or less evenly between Ukrainians who see Ukraine as part of Europe and those who see it as intrinsically linked to Russia. An internal political crisis over that disagreement may have been inevitable. Meanwhile, in Russia, Putin is pushing an imperial-revival, nationalist worldview that sees Ukraine as part of greater Russia — and as the victim of ever-encroaching Western hostility.

It appears unlikely that Ukraine will get Crimea back. It remains unclear whether Russian forces will try to annex parts of eastern Ukraine as well, how the fighting there will end, and what this means for the future of Ukraine — and for Putin's increasingly hostile but isolated Russia.

https://www.vox.com/2014/9/3/18088560/ukraine-everything-you-need-to-know

"I have nothing against Russian nationalists, or a great Russia," said Dmitry, as we sped through the dark Mariupol night in a pickup truck, a machine gunner positioned in the back. "But Putin's not even a Russian. Putin's a Jew."

Dmitry – which he said is not his real name – is a native of east Ukraine and a member of the Azov battalion, a volunteer grouping that has been doing much of the frontline fighting in Ukraine's war with pro-Russia separatists. The Azov, one of many volunteer brigades to fight alongside the Ukrainian army in the east of the country, has developed a reputation for fearlessness in battle.

https://www.theguardian.com/world/2014/sep/10/azov-far-right-fighters-ukraine-neo-nazis