Russia's energy weapon

Russia recently cut off natural gas supplies to Ukraine and Moldova. Gazprom is a state-owned monopoly; it's the Russian government calling the shots

There is probably some truth to Ukraine's claim that it is being punished for developing closer ties to the West and becoming more independent of Russia. It's worth recalling that the Russian national firm Yukos was effectively destroyed and a primary asset sold to a shell company later acquired by state-owned Rosneft; due to the timing, it appears Yukos was targeted in order to prevent the company from from joining Western firms in a merger.

It is clear that Russia's current main strength is its capacity to use energy as a weapon, not the projection of military power. A logical consequence of this is the scenario that Russia did intend for UN negotiations to fail and for the USA to lead an invasion of Iraq. Even a temporary loss of Iraqi oil supply would certainly increase Russia's bargaining position.

Russian nationalism appears to be a significant motivation:

Global energy supply is set to be a big issue, with Russia seeking to show the importance of its oil and gas reserves...
Mr Putin has made restoring Russian prestige central to his presidency.