After the 1917 February Revolution in Russia, the Belarusian language became an important factor in political activities in the Belarusian lands ("see also:" Central Council of Belarusian Organisations, Great Belarusian Council, First All-Belarusian Congress, Belnatskom). In the Belarusian People's Republic, Belarusian was used as the only official language (decreed by Belarusian People's Secretariat on 28 April 1918). Subsequently, in the Belarusian SSR, Belarusian was decreed to be one of the four (Belarusian, Polish, Russian, and Yiddish) official languages (decreed by Central Executive Committee of BSSR in February 1921).