Austria-Hungary gave Serbia an ultimatum, the terms of which Serbia did not entirely except. Therefore, Austria-Hungary declared war on Serbia. None of the powers could find a way to avoid war. Russia had lost many times, and so they took action. They had to support Serbia. This is how they became involved in WWI. Russia mobilized against Austria-Hungary and Germany. Germany gave Russia an ultimatum, and Russia had to stop its movements. Germany also gave France an ultimatum. France decided to support Russia. Germany declared war on both Russia and France. Russia sent troops to invade East Prussia from the south and east. Russia did not fare well though. Germany accidentally found plans of the Russian army's movements, as well as uncoded messages, and intercepted them. Over 92,000 Russians were taken prisoner, and more than 30,000 were killed. Russians did not like that they were in the war, and many wanted for Russia to withdraw.
Civilians were negatively affected by the war. By 1917 the Russian soldiers had practically no morale. There were also food and weapon shortages. To make things worse, there were riots and food shortages in Russia. The Tsar Nicholas' government fell, and a temporary one was established in its place. Lenin, who had been in exile in Switzerland, came back, and the Bolsheviks took over the Russian government. They wanted to end Russia's participation in the war. On March 3, 1918, the Treaty of Brest-Lotovsk was signed by Russia. It said that they agreed to give up Finland, Poland, the Baltic States, and a large part of the Ukraine to Germany. That is summary of Russia in WWI.