Finnish support of the uprising with volunteers and humanitarian aid caused a notable regression on Finnish-Russian diplomatic relations. Leon Trotsky, the commander of the Red Army, announced that he was ready to march towards Helsinki and Soviet Russian troops would strike the East Karelian rebels with a 20 000 strong army via the Murmansk railway. At the onset of winter, the resistance of Forest Guerrillas collapsed under superior numbers of the Red Army, famine, and freezing cold. The rebels panicked, and their troops started to retreat towards the Finnish border. According to Shirokorad, the troops of the Red Army had crushed the main group of the Finnish and Karelian troops by the beginning of January 1922 and had retaken Porosozero and Reboly. On January 25, the northern group of the Soviet troops had occupied Kestenga and Kokkosalmi, and by the beginning of February occupied the settlement Ukhta. During the final stages of the uprising, the Red "Pork mutiny" occurred in Finland, sparking a hope among the rebels and Finnish volunteers that this would cause the Finnish government to intervene and provide military aid to the insurgents. This did not happen; on the contrary, the minister of interior, Heikki Ritavuori, tightened border control, closed the border preventing food and munitions shipments, and prohibited volunteers to cross over to join the uprising. The assassination of Ritavuori on February 12, 1922, by a Finnish nationalist activist did not change the situation. The last unit of the uprising, remnants of Viena Regiment, fled Tiirovaara on February 16, 1922, at 10:45 am and reached the border at 1 pm.
Question: What was used to strike East Karelian?
Answer: Murmansk railway