Unfortunately, most of the answer bring in the propaganda of their own political view. I will try to avoid that in the following. For this, I've structured my answer as follows:
- Theories of International Policy
- Russian interests in Ukraine
- Possible Russian prevision
and at the end a fun appendix with a Chess analogy ;)
1. Theories of International Policy
Basically, one could approach this problem by the various theories of International Policy that are, among others, the Realist, the Liberal/Idealist, and the Marxist influenced traditions, which is roughly congruent with the political triangle conservative/liberal/socialist.
Just a summary for the former two:
the Realist approach supposes that states always want more (not less) power, and act rational to achieve this,
the Liberal/Idealist approach rejects this Machiavellian view of international policy, and puts rather universal values in the focus (bringing democracy to the world). In this view, the outer actions of states also mirror their inner political philosophy.
These two are probably the more relevant ones to the conflict here, mainly because they are more influential than the Marxian views (World-systems theory, Neo-Gramscianism), so that it is unlikely that the Russian actions were motivated by them.
Back to the Realist/Idealist divide: this is not necessarily congruent with the division hawks/doves. It is not unusual that Realists object to wars that are supported by Idealists! Now, often one hears the term Neoconservatives in context of American Foreign Policy; it is difficult to characterize them in those traditions, but I would propose that essentially they put an Realist agenda hidden by an Idealistic camouflage. But that would be a question on its own.
Coming back to the main question, one has to first decide which of these two ideologies the Russian foreign policy establishment subscribes to. I think that almost no one would argue that the Russian foreign policy has some Idealist elements that go much beyond a clumsy cover (or, alternatively the laughable claim that the evilness of a power-hungry Czar Vladimir I. Putin in domestic politics clearly shows his evil intentions in international relations). Therefore, assuming a Realist Russian approach is appropriate here.
2. Russian interests in Ukraine
Having established a Realist point of view of the Russian foreign policies, we need to identify the Russian interests in Ukraine. These can be split in different subgroups:
- Economic ties
- interdependence of economies in foreign trade: this was quite considerable before the conflict
- delivery of gas from Russia to Ukraine
- Macroeconomic issues: Russia argued that Ukraine could not be simultaneously member of two free trade zones, one with Russia and one with the EU. The basic argument is that now Russia can guard its industries by imposing tariffs on EU-products, while if Ukraine joins both free trade zone, EU-based companies could flood the Russian market via import-export companies located in Ukraine, thereby destroying uncompetitive industries in Russia. These were actually the arguments that pressured Yanukovich to reject the European offer which led to the Maidan protests in the first place. See also the answers to this question.
- Military ties
- Direct military cooperation
- Ukrainian armament factories that are supplying the Russian Army
- Military-Strategic issues
- Sea access via Sebastopol: the Russian marine has long term leasing agreements for the use of the naval base located there. This is a major strategic issue
- encirclement by NATO
Maybe there is even more. I haven't provided references for these points and also I didn't classify them by their importance, as it is difficult to judge which of these factors were important to Russian consideration. H
3. Possible Russian prevision
It is also quite reasonable to assume the Russian leadership knew what is at stake by engaging or not engaging in conflict.
In the list above are several points which show that Russia has quite some economic relation with Ukraine that it would surely loose as soon as a conflict starts.
Therefore, it is highly unlikely that the Russian move was preplanned and just waiting for a favourable occasion.
So the conclusion must be that the Russian government looked at the situation in the post-coup Ukraine (or call it post-revolution if you are pro-Maidan), and assessed the prospects of having their interests still supported by the new government. As the political leaders of the Maidan were pro-European or pro-Western (Klitschko was sponsored by German political foundation, Yatsenyuk directly by American think tanks), the outlook was dim. Especially the fact that Yatsenyuk publicly denounced the leasing deal of the Sebastopol naval base by the Russian marine surely has spawned major concerns in the Russian military establishment, see also this answer. In my opinion this was really the tipping point for the annexation of Crimea.
The possible counterargument for this is the swift reaction of the Russians. However, these scenarios are all planned and played through in the foreign policy think tanks. An striking example is the following report (pdf) of a so-called Policy Game at the German Körber Foundation, which considered the opposite case of western Ukraine becoming separatist upon the Yanokovich government joining the EAU. EAU means here the free trade zone with Russia.
The Körber Policy Game “Crisis Management in Eastern Europe” was held against this backdrop in Berlin from May 3 to 4, 2013. The discussion was based on a hypothetical three-stage scenario. In this the Ukrainian government, which is faced with a faltering economy, feels compelled to join the EAU. The decision leads to mass protests and to a declaration of independence by the ten oblasts to the west of Kyiv, which now call themselves “West Ukraine.” The participants in the Körber Policy Game were four national teams (Germany, Poland, Russia and the US), each of which included between four and six high-ranking politicians,
government representatives and experts from the respective countries. In internal team sessions they discussed the interests of their countries and devised tactical and strategic recommendations to take action that were subsequently discussed with the other participants in the Körber Policy Game.
To me this document is an eye-opener that really shows that just a few months before the Maidan the Great Powers discussed openly how their strategies and reactions would be if an event similar to the Maidan and the Donbass separatist movements would occur. So surely the Russians thought about the prospects of their future interests as soon as the first Maidan demonstrations occurred and weighted them after an intervention in Crimea.
So some planning obviously took place beforehand, but the events seems to me clearly been triggered by the Maidan uprising.
Fun Appendix: Chess analogy
Rephrasing your question in terms of Chess, it would be:
Was the Russian intervention in Ukraine more like
- a pawn sacrifice where Russia could beat the opponent's knight, or
- a move of Russia loosing a knight after been confronted to a Gardez?