Read this article and answer this question The Czechoslovak Legion fought with the Entente; its goal was to win support for the independence of Czechoslovakia. The Legion in Russia was established in September 1914, in December 1917 in France  and in April 1918 in Italy. Czechoslovak Legion troops defeated the Austro-Hungarian army at the Ukrainian village of Zborov, in July 1917. After this success, the number of Czechoslovak legionaries increased, as well as Czechoslovak military power. In the Battle of Bakhmach, the Legion defeated the Germans and forced them to make a truce. In Russia, they were heavily involved in the Russian Civil War, siding with the Whites against the Bolsheviks, at times controlling most of the Trans-Siberian railway and conquering all the major cities of Siberia. The presence of the Czechoslovak Legion near Yekaterinburg appears to have been one of the motivations for the Bolshevik execution of the Tsar and his family in July 1918. Legionaries arrived less than a week afterwards and captured the city. Because Russia's European ports were not safe, the corps was evacuated by a long detour via the port of Vladivostok. The last transport was the American ship Heffron in September 1920.
How many years after the Bolshevik execution of the Tsar and his family did the last transport evacuate the area?
2