I'd say Russia was already on the brinks of Civil War in 1905.
The people had enough of the Nobility's oppression and back then were still living with a way outdated set of society, and so, were heading to St-Petersburg to demand changes to the Czar Nikolai II from the Romanov Dynasty.
Unfortunately the Czar wasn't even in town at that time while the people's protests heading to the Czar's palace were lead by some members of the Orthodox Church.
For a reason that remains unclear, the Czar's Guards opened fire on the crowd that day which remains known in Russian History Books as the Red Sunday Massacre.
Red the color of blood as sounds fitting to a massacre such as this one.
Soon beyond that, Russia delared War on Japan whose Navy took out the entire Russian Pacific Fleet docked in the Port-Arthur base in China.
During that time, the Russian High Command decided to send the Baltic Fleet under Admiral Rojyestvensky (Don't know how to spell it) to fight the Japanese. The Russian Baltic Fleet's flagship was known as the Kniaz Suvarov. But the Russian Sailors were in no mood to fight and the Morale was already down among Russian Sailors.
Following a very long trip, the Russian Baltic Fleet was ambushed by the Japanese Fleet under Admiral Heihachiro Togo's Command in what became known as the battle of Tsushima.
The entire Russian fleet was sunk, except a handful of small warships which made it to Vladivostok and Admiral Rojyestvenky had surrendered to the Japanese.
However, as the Russian High Command was planning to send the Black Sea Fleet, the Battleship Potemkin Incident occured with the entire crew revolting against their Commanding Officers.
And as a result, the Black Sea Fleet wasn't sent to the Pacific and Russia had suffered a humiliating defeat in 1905.
Russia was still in a state of unrest following the defeat against Japan, with many riots, and key political figures who would be well known in the future.
Back then, a new underground Newspaper which was born from Karl Marx's ideals and which would be known as the Communists Official Newspaper lead by men such as Vladimir Illich Ulianov better known as Lenin, Leon Trotsky, and Josef Vissarionovich Djugachvilly better known as Stalin was spreading the seeds of revolution through all Russia known as The Pravda (Meaning: The Truth in Russian). Obviously the Pravda had been branded as "Illegal" and Subversive by the Government.
In 1914, it was Russia declared War on the Austrian-Hungarian Empire resulting Germany declaring War on Russia.
The Russians were already lacking many Military supplies, and the Heir to the Throne in Russia was suffering a severe case of hemophilia.
This is where a Monk from Siberia entered the scene known as Rasputin.
While just many Doctors few people such as the Czar could afford had given up on the Prince, Rasputin had conned the Russian Queen into telling her that as long as he (Rasputin) would be around, the Prince would still be alive.
Yet during World War One, the Russian Queen was already very unpopular because before becoming the Queen, she was a German Princess. And of course Rasputin's very presence made things even worst for the Czar and his entire familly.
After many Battles against the German Forces such as the Battle of Tannemberg, things were looking very bad for the Czar and so, he decided to take command of the entire Russian Army himself.
Back in Russia, the Queen was left in charge of everything there, and mostly took decisions basing herself on Rasputin's advice.
Then, some Russian Noblemen decided to assasinate Rasputin since they felt the situation was intolerable. At first they had him take massive doses of poison yet Rasputin survived, after seeing poison wouldn't do the job, they had him shot and threw his corpse in a river. still according to what the autopsy revealed, even the guns didn't killed Rasputin, what did killed him was because he drowned.
In 1917, the Revolution occured in Russia and the Czar had to pull out from his War against Germany even if that meant losing many territories. After an agreement was signed, the Czar did let his people have a say on his decisions so the Duma (Note: I'm not sure of when the Duma Assembly was really set up) was created and the Czar had no choice but to step down.
A Provisional Government was then set to rule Russia, however later on a coup d'état lead by Lenin and his gang took over the place.
Some of the Army were still loyal to the Czar and his familly, the rest sided with Lenin. Meanwhile, countries who much preffered having the Czar around than the Communists sent troops to fight alongside the troops still loyal to the Czar (Japan, France, the British Empire mostly).
This is what I heard were the origins of the Russian Civil War.