I was reading the biography of Winston Churchill by Dr Martin Gilbert, and had got to volume IV (yes, Churchill's life is so full it requires umpteen volumes to cover it), and came across this quote from Churchill about what happened in the Bolshevik Revolution:
Lenin was sent into Russia by the Germans in the same way that you might send a phial containing a culture of typhoid or cholera to be poured into the water supply of a great city, and it worked with amazing accuracy
Russia had two revolutions in 1917. The first revolution, the February Revolution was a normal revolution against the Tsar for mismanagement of both WW1 and the domestic front. The "revolutionaries" were the middle classes who wanted to establish a Parliamentary democracy of the sort they had in Britain and France. They persuaded the Tsar to abdicate and set up a provisional government to stabalise the country and write a new constitution.
So far so good.
But Russia was allied with Britain and France against Germany in WW1, and the Germans, seeing an opportunity to completely destabalise Russia and remove it from the theatre of war, mobilised their weapon - Lenin.
Lenin had been in exile in Switzerland - so he and his acolytes hadn't participated in the February revolution at all. He was given a shedload of gold by the Germans and put on a train to Russia, where he arrived in April and immediately started to undermine the provisional govt.
He claimed that Alexander Kerensky, the leader of the new provisional govt, was a complete failure for not immediately solving the problem of supply of food and jobs.
Initially the Russians ignored Lenin, but by August the Bolsheviks persuaded some in the army to start to move against the new govt. The Bolsheviks then managed to "persuade" the army general Kornilov to stand down, and then claimed that they were therefore more effective at maintaining order than Kerensky. The October Revolution followed, which gave the Bolsheviks and Lenin complete control.
One of the first things Lenin did when he took power was issue a "Decree of Peace" where Russia not only unilaterally withdrew from WW1, but conceded to Germany all the German conquests (Poland, Lithiuania etc). In the treaty that was signed, Russia conceded 26% of the former Empire's population, 37% of its agricultural harvest area, 28% of its industry, 26% of its railway tracks, and three-quarters of its coal and iron deposits to the Germans.
The Germans then turned to their western front, certain that they were going to win the war. (Part of the resentment in Germany after 1918 was down to the population not quite believing that they'd actually lost after coming so close to a total win).
As for poor Russia - their brief window of opportunity for a parliamentary democracy was snuffed out. They struggled under the brutality of communism till 1990, and then struggled under the aftermath ever since. It's just over 100 years since these events and Russia still hasn't really established the stable parliamentary democracy they were so hopeful of before Germany released the virus of communism into their system.