If It Comes to War: The Military Balance of Power
I’m not going to go into numerical details of the military balance between Russia and Ukraine. Suffice it to say that on paper Russia has overwhelming superiority, particularly in aviation and advanced armored vehicles., but also in numbers. You can find the raw figures all over the web now.
Overall, the Ukrainian Army disposes of a good deal of obsolete hardware and many under-trained troops. Certainly most Ukrainian units do not approach the combat readiness of elite Russian forces. In addition, the Ukrainian military has been in an awkward and extended transition from a Soviet style force oriented towards mass armored offensive warfare (highly coordinated conventional tank attacks supported by aviation aimed at rapid, deep penetration behind enemy lines) and a more flexible defensive force with more 21st century doctrine and technology, and smaller, more easily deployed units (brigades rather than divisions).
We can talk about three scenarios of military conflict between Russia and Ukraine.
1. An assault of Russian forces on Ukrainian bases in the Crimea — a possibility in prospect within hours. According to Ukrainian news sources, many if not most Ukrainian units in the Crimea are ready to resist. Russian and Western sources suggest otherwise. In any event, the Russian units now deployed in the area are far superior to the Ukrainian. Any resistance would be hopeless — loyal Ukrainian commanders may choose to put up a token resistance and surrender quickly. The Ukrainian commanders on the spot are in an even worse position than this suggests, as Kiev presumably does not want large-scale fighting in the Crimea which could provide the Russians a pretext for incursions into east Ukraine, or even an all-out invasion. In short, I expect that within 24 hours there will be no Ukrainian military presence in the Crimea, and that this will be accomplished almost if not entirely without bloodshed.
2. A limited Russian incursion into east Ukraine, under the pretext of protecting the regional Russian population. Ukraine would be in a very poor position to resist this move. The bulk of the Ukrainian Army is stationed in the west, and at least some Ukrainian units in the east can be expected to defect or surrender. On the open steppe, which is the dominant terrain in the east, units which did resist would be quickly surrounded and overwhelmed by Russian mechanized assault supported by air superiority.
3. An all-out Russian invasion of Ukraine, with the aim of installing a pro-Russian government, under the pretext that the new Kiev government is “fascist”. Russia would win this war if it was determined to bear the international consequences. However, the terrain in west Ukraine is more difficult, and the bulk of the Ukrainian Army is stationed here. The Dnepr River is a geographical barrier to Russian advances as are the mountainous and forested regions of far western Ukraine and the huge swamps in northwestern and north central Ukraine. The Russians would face an overwhelmingly hostile population. There would probably heavy resistance in the cities, with irregular forces playing an important role. Russian experiences in the Chechen capital of Grozny might well make commanders wary of this kind of battle. Russia could win such a war, but at a relatively high cost in casualties and international standing.
One possible move that NATO might take is to send a few troops into western Ukraine (small NATO forces have participated in numerous joint military exercises there) and dare the Russians to attack them directly. This would, in my opinion, be a substantial deterrent to a Russian invasion.
In short, an all-out Russian invasion of Ukraine is highly unlikely.