About time these arguments become public:

https://www.economist.com/christmas-specials/2021/12/18/why-russia-has-never-accepted-ukrainian-independence

In “Rebuilding Russia”, an essay published in the USSR’s most widely circulated newspaper the year before, Alexander Solzhenitsyn had asked “What exactly is Russia? Today, now? And—more importantly—tomorrow?…Where do Russians themselves see the boundaries of their land?” The need to let the Baltic states go was clear—and when they left the Soviet Union in 1990, Solzhenitsyn, Yeltsin and most of Russia rallied against revanchist attempts to keep them in. Much the same was true of Central Asia and the Caucasus; they were colonies. Belarus and Ukraine were part of the metropolitan core. The bonds which tied “Little Russians” (ie Ukrainians), “Great Russians” and Belarusians together, Solzhenitsyn argued, must be defended by all means short of war.

For centuries Ukraine had anchored Russia’s identity. As the centre of the storied medieval confederation known as Kyivan Rus, which stretched from the White Sea in the north to the Black Sea in the south, Kyiv was seen as the cradle of Russian and Belarusian culture and the font of their Orthodox faith. Being united with Ukraine was fundamental to Russia’s feeling of itself as European. In “Lost Kingdom” (2017) Serhii Plokhy, a Ukrainian historian, describes how “the Kyivan myth of origins…became the cornerstone of Muscovy’s ideology as the polity evolved from a Mongol dependency to a sovereign state and then an empire.” Russian empire required Ukraine; and Russia had no history other than one of empire. The idea of Kyiv as just the capital of a neighbouring country was unimaginable to Russians.

But not to Ukrainians.