Lawrence Freedman argues that 'The basic challenge of crisis management is to protect core interests while avoiding major war'. He lists some major lessons from the Ukrainian crisis:

One main difference between Cold War crisis management and the 21st Century is the importance of the economic dimension.

There was very little interaction between East and West during the Cold War. The export of energy was one area which began to grow during the Cold War and then became progressively more important. In 2007 and 2009 gas supplies were cut off to Ukraine and this affected European suppliers using the same pipeline. The position has changed substantially over the past few years. The Russian economy is now slowing down and Gazprom’s position is no longer so buoyant. Both need the revenues. Russia has chronic problems of demography and corruption.  It has failed to move its economy away from being dominated by oil and gas, and become an increasingly unattractive place to invest. It is not an emerging economy but a declining one. The past use of gas supplies for coercive purposes has encouraged customers to look elsewhere or to develop alternative supplies so they are less vulnerable to coercion. Finally, the transformation of the US’s energy position over past few years could be used to weaken Russia’s position further. One response to the crisis has been a determination to further move away from dependence on Gazprom. The long-term significance of this should not be underestimated.

Chicago Law School professor Eric Posner, meanwhile, examines the legal arguments in Vladimir Putin's recent speech to the Duma (Posner's comments in bold):

We keep hearing from the United States and Western Europe that Kosovo is some special case. What makes it so special in the eyes of our colleagues? It turns out that it is the fact that the conflict in Kosovo resulted in so many human casualties.  Is this a legal argument? The ruling of the International Court says nothing about this. [True; it is legally irrelevant.] This is not even double standards; this is amazing, primitive, blunt cynicism. One should not try so crudely to make everything suit their interests, calling the same thing white today and black tomorrow. According to this logic, we have to make sure every conflict leads to human losses. [The U.S. position is that forcing Kosovo's population to remain a part of a country whose government tried to massacre it would be wrong, and numerous efforts were made to broker a compromise before secession took place. Putin argues that it would be ridiculous to make Crimea wait for its population to be massacred before seceding.]

I will state clearly – if the Crimean local self-defence units had not taken the situation under control, there could have been casualties as well. [This is doubtful, as there were no massacres anywhere else in Russian-speaking Ukraine that did not benefit from "local self-defense units".]

Stewart Patrick says the legal arguments are a distraction.