In 1954, when the Ukraine was the Ukrainian SSR of the Soviet Union, Nikita Khrushchev literally gifted the Crimea to Ukraine as part of an internal USSR political deal to secure the support of the Ukrainian party bosses for his succession following the death of Stalin.
This was a purely internal USSR political gift with no international consequences in the 1950s. The Soviet military bases remained Soviet military bases. Khrushchev's unilateral political gift was of no concern to the world until the breakup of the USSR.
The way that Russians see the situation is that Putin is undoing Khrushchev's blunder. What Khrushchev gave away, Putin is taking back, and returning to the Russian fold.
It's important to understand this history. Crimea is the location of Russia's all-weather naval bases, and has been for over 200 years. The fluke of "Ukrainian Crimea" only lasted from 1954 until 2014, sixty years, a blink in historical terms. Before Khrushchev's unilateral political gift, Crimea was never part of Ukraine for one single day in recorded history.
Imagine a dictatorial President Eisenhower, on his own, "giving" NYC and Long Island to Connecticut in return for CT electoral college votes to assure his election. That is how Crimea was transferred to Ukraine in 1954.
Now, Putin is a KGB Soviet Gestapo thug, leader of assassins, and probably the greatest thief in history. But it's important to get the history right in order to avoid mistaking the situation for something it is not, and blundering into a major war. Crimea is not analogous to Latvia, Poland, or even the rest of Ukraine.
