On 25 March 1918, a small group of Belarusian nationalists declared the formation of a Belarusian People's Republic. Although, less than a year later, the Soviets claimed the same territory for a Byelorussian Soviet Socialist Republic. In 1921, the Peace of Riga was signed, which officially divided the Belarusian lands between Poland (Western Belorussia) and the Soviet Union (Eastern Belorussia). The Polish government engaged in a Polonization policy in Western Belorussia, therefore a sporadic partisan warfare against Polish authorities occurred until the mid-1920s, which was also supported by Lithuania, because it fought the Polish–Lithuanian War (part of the Lithuanian Wars of Independence).