Not the most important political issue in the world, and not central to the politics of the original article, but just to defend the sentence:
“For the first time since the Second World War the territory of a European country has been seized by that of a neighbouring big power.”
Crimea is now, since March, a “federal subject” of the Russian Federation. It was previously part of the sovereign state of Ukraine. But now it is a fully integrated part of the sovereign state of Russia.
None of the other invasions mentioned by Eric resulted in actual sovereignty over a piece of land being formally transferred from one state to another.
Stalinism certainly controlled Hungary and Czechoslovakia. But they did not end up, post-invasion (1956 and 1968), as the equivalent of a federal subject of the Russian Federation, i.e. they were not formally integrated into the Russia or the Soviet Union.
Northern Cyprus is occupied by Turkey and claims to be independent. But not even Turkey claims that it is part of Turkey.
Chechnya attempted to go independent when the Soviet Union broke up but was eventually defeated. It was never the territory of another European country which was seized from that country and then incorporated into Russia. Russia ‘simply’ refused to allow it go independent.
South Ossetia and Abkhazia both claim to be ‘independent’, following Russian military aggression. But neither have been incorporated into the Russian Federation as federal subjects. (The same also applies to the Transnistrian Republic of Moldova.)
So, what distinguishes Crimea from all the other instances cited is not military invasion and occupation – which certainly also happened in the other cases cited by Eric – but the fact that it ended up being fully integrated into Russia, having previously been part of a different sovereign state.