Russia has expanded its territorial claims beyond Ukraine to includes what it calls Greater Russia. This is not quite the rebuilding the tsarist or communist empires because Russia does not want the expensive (to rule) Central Asian states, but rather more lucrative territories Russian once ruled. This includes portions of Poland, the Baltic States, Finland and parts of Alaska. There are some serious legal and practical problems with these claims. The United States has a larger military and nukes with which to dispute any Russian claims on Alaska. Russia is making claims on several Eastern European NATO members who are protected by the mutual defense clause of the NATO treaty.
Russia and all the nations involved are members of the United Nations. Article 51 of the UN charter demands that members refrain from the use of force against the territorial integrity or political independence of any state. Russia says this does not apply because Ukraine is a breakaway part of Russia and Russian troops are seeking to liberate Ukraine from foreign (NATO) oppression. Ukraine is also a UN member and protests Russian claims as well as the UN tolerating the Russian use of its Security Council veto to block any serious UN opposition to the Russian aggression.
What really blocks Russian annexation efforts is the Ukrainian determination to regain all territory currently occupied by Russia no matter what the cost. Russia is using classic police state tactics to prepare the occupied Ukrainian territories for a vote that will vote to join Russia no matter what the original occupants want. Russia will not allow the UN or any other foreign observers. The theory behind this is that if Ukraine does regain control of these areas Russia is justified as declaring itself the official victim of foreign aggression. This might encourage more Russians to back the war effort. If there is no such increase in support, Russia can double down by claiming most Russians do indeed back Russian claims that these occupied areas are now part of Russia.
All this is a major gamble by the current Russian leader (Vladimir Putin) who has been facing more domestic opposition the longer the Ukraine operation continues. Putin sees his main effective weapons as threats and disinformation used against his many opponents to cause uncertainty and indecisiveness. If NATO can be persuaded to break ranks on its support of Ukraine Russia has a chance to succeed. It’s that prospect that is the key to maintaining NATO unity and growing UN opposition to Russia. It’s still an endurance contest and will remain so until one side backs down.
The main propaganda problem for the Putin strategy is the growing opposition of civilians in Russian occupied Ukraine. Currently Russia is trying to find enough local collaborators to allow convincing propaganda videos. This effort is disrupted by the widespread and often violent resistance to the occupation, local collaborators and efforts to stage a fake election. Russian efforts to cut occupied areas off from the outside world have been energetic but not enough. Replacing Ukrainian cell phone service with Russian based service is not enough. Civilians will risk arrest and worse by keeping their Ukrainian cell phones to collect and smuggle out videos of what is really going on. This includes threats, sometimes carried out, to cut electrical service and access to clean water. Threats were made to tank children from families and send the kids to Russia as hostages. The Ukrainians realize that if they can get video evidence of such threats or actions out, the Russians will be forced to back down. For many people inside Russia these tactics are not acceptable, especially when so many Ukrainians obviously see the Russian troops as invaders, not liberators. This has turned many Russians against their own government. This is nothing new as it happened in 1991 and several other times in the last century. Bad behavior by aggressive Russian governments is the main reason NATO exists and Ukraine wants to join it.