Yes I believe that defeat is inevitable, I also believe Russia has to be paying a large price for taking Ukraine, lots of expenses in manpower and military hardware that they cannot easily replace.
The EU will have to build up a military and NATO will have to build up theirs.
There is no escaping an arms race at this point because incompetent politics have led the world to this point on both sides.
Russia is not "taking Ukraine". With a Ukraine defeat Dunbas remains independent, as they declared eight years ago.
I suspect Russia's losses are a lot less than most believe, and that those of Ukraine and its Western suppliers will prove to be far greater. Here's why...
Standard military doctrine calls for an attacking force that is three times the strength of the defender. Russia was capable of crushing Ukraine with overwhelming power, but it chose to apply a very limited force that was outnumbered 3:1 by the Ukrainian Army - a clear indication that Russia never intended to take all of Ukraine. In three months, this smaller force has managed to:
- fix the Ukrainian Army along a long eastern front;
- divert Ukranian reserve forces to the north in a feint against its capital city, which was never attacked;
- draw other Ukrainian reserves to southwest to block Russian advances from Crimea; and
- wage a two month air and missle campaign to destroy Ukraine's air force, cripple its military logistics and transport capabilities, and isolate the bulk of Ukraine's combat power in the east.
Now Russia is waging a devastating artillery war that is chewing up the increasingly demoralized Ukrainian Army. Time is on Russia's side, which explains the growing panic in Kiev, Berlin and Washington.
Poland is mobilizing its army to seize the remainder of its historic territory of Galicia (which includes the present Ukrainian oblasts of Lviv, Ternopil and Ivano-Frankivsk) as soon as the Ukrainian Army collapses. Most people have forgotten that Poland and Ukraine fought a war over Galicia back in 1918-1919, but Warsaw never forgot. Ukraine will emerge from this war landlocked and much smaller.