The revolutions began in Petrograd, now Saint Petersburg, while Moscow became a central seat of Bolshevik power. Civil war spread across European Russia, Ukraine, the Caucasus, the Volga region, Siberia, Central Asia, and the Russian Far East. Foreign forces intervened at ports including Arkhangelsk, Murmansk, and Vladivostok. Vast distances, railway corridors, major rivers, and harsh seasonal conditions strongly influenced the movement and supply of armies.