History / Mother tongue in Poland - acccording to 1931 census. [174]

My grandfather was born in Ropczyce in 1900 and fought in the war against Russia. After the war, probably in 1922, he moved to a city near Tarnopol, where my father was born in 1925. Could anybody tell me what were the government promisses to ex-soldiers in order they could leave their hometowns and go eastern beyond the Bug River?