In the summer of 1941 Hitler launched Operation Barbarossa, a surprise invasion of the Soviet Union. It was the largest military invasion in history, involving more than three million German soldiers, and eventually included forces from Hitler’s fascist allies Italy, Romania, Hungary, Slovakia, and Croatia.
The Ukrainian Soviet Socialist Republic was one of the first areas conquered by the Germans. The German victory encouraged the Organization of Ukrainian Nationalists (OUN). The OUN had been organized in Western Ukraine in 1929 to protect ethnic Ukrainians and establish an independent Ukrainian state by any means necessary, including the use of violence. It was a fascist organization, but Hitler opposed Ukrainian nationalism so he ruthlessly suppressed them.
Despite this, by the fall of 1943 the OUN had created an effective guerrilla army, called the UPA. It attacked the German occupation forces until the spring of 1944, and then decided the advancing Soviet army was a bigger threat to Ukrainian nationalism and began fighting against the Soviets, with help from the Germans. The UPA continued fighting the Soviets even after the Germans had retreated from Ukraine, and kept on fighting them after the end of World War II. The Soviets weren’t able to completely eliminate the UPA until the mid 1950s.
The modern day Congress of Ukrainian Nationalists, a far-right Ukrainian nationalist political party, consider themselves descendants of the OUN, and they use the UPA’s red and black battle flag. The Russians, as you would expect, were disturbed to see this flag being carried by some protestors during the recent political upheaval in Ukraine.
The Russians are also very concerned about Western involvement in Ukraine. The 1941 fascist invasion came from the West, and the Soviet Union suffered at least 26 million dead in World War II, and maybe as many as 40 million. More Soviet soldiers, for example, died during the battle of Stalingrad than were killed in all of the U.S. armed forces during the entire war. Furthermore, even though the Allies sent the Soviets lots of supplies, they failed to open a promised second front in Western Europe until the D-Day invasion of France in the summer of 1944. World War II is called the Great Patriotic War in Russia and every Russian politician since then has promised the Russian people they would never let anything like that happen again.
The Crimean peninsula, where Russian forces took over February, was traditionally a Russian area. It only became part of Ukraine in 1954, and most of its residents still speak Russian. The Crimea is also home to a very important Russian naval base in Sevastopol, a port on the Black Sea. Sevastopol was subjected to a siege by the invading Germans and their Romanian allies in World War II. Soviet forces held out heroically for several months before finally surrendering in July of 1942 after suffering enormous casualties. The Russians have a lease allowing their fleet to use Sevastopol until 2042, but it’s easy to see why they’re worried the new Western-oriented Ukrainian government might cancel it.
Considering their national history, it’s difficult to entirely condemn the Russians if all they’re trying to accomplish with their annexation is to protect ethnic Russians and their perceived national defense interests in the Crimean peninsula. But if they invade the rest of Ukraine, that’s a different thing altogether.
In April, 2014, pro-Russian separatists seized Ukrainian government buildings in the Donetsk and Luhansk regions, often called the Donbass, along the Russian border and proclaimed the Donetsk and Luhansk People’s Republics . War broke out with the Ukraine and the separatists were subsequently provided with military support from Russia, helping them to continue control of areas along the border. Economic sanctions were subsequently imposed by the U.S. and many other nations against Russia for its annexation of Crimea and its support for the Donbass separatists.
On February 11, 2015, a peace treaty called Minsk II was signed that ended most of the fighting between Ukraine and the pro-Russian separatists in the Donbass.
On November 26, 2018, Russia seized seized 23 Ukrainian sailors and three of their naval vessels when they tried to pass through the Kerch Strait, which is only about 2 miles wide. The Russians claimed it was a violation of their territory. The Ukrainian government responded by declaring martial law and banning Russian men aged 16-60 from entering the country.