Early in the war Lukashenko showed a battle map showing all the places where Russian was planning to attack Ukraine from, and one those place was a Russian controlled Moldova. In reality Russia needed a Ukrainian land bridge to Transnistria to make an invasion possible but Ukraine never let Russia take that much territory.

There's another interesting idea I heard that Putin was actually planning on conquering or subduing Ukraine, then he was going to mobilize Russia to get the military he needed to take on the other countries on his list (Moldova and Belarus would have been the safest bets for the next two countries he would have annexed), but in either case Ukrainian resistance forced him to move up his mobilization schedule before he was ready.