At the start of the Civil War, the Bolsheviks controlled the key central area of Russia between Petrograd and Moscow. This gave them a number of advantages.
Most of Russia's railways were in this area. This made communication between the various battlefronts much easier. Trotsky was able to move troops and supplies quickly to positions under attack. As Commissar for War, he was able to visit the battlefronts in an armoured train, and to take personal command.
The large population of the major cities was a key resource for the Bolsheviks. The cities provided fresh recruitment for the Red Army.
Much of Russia's industry and raw materials was located in this area. This made it possible for the Bolsheviks to keep their troops supplied and equipped with weapons, ammunition and supplies.
The sheer size of Russia worked against the White Armies. They had to move their forces and supplies over huge distances. This made it difficult to maintain effective control.
The lack of effective railways was an added complication to the existing communication difficulties between the different White Armies and their leaders.
By the end of the Civil War in 1921 the Bolsheviks had succeeded in securing their grip on power in Russia.
The White Armies and the foreign powers fighting on Russian soil had been defeated. Just as importantly, rival political parties had been outlawed. Thanks to the Cheka secret police, dissenting voices had been silenced.
Lenin had achieved his ultimate goal of steering his small Bolshevik party to total control of Russia.