sentences:  With Denikin launching an offensive against the Reds in the north, along with spontaneous peasant uprisings allowed the Ukrainians to retake Kiev in August 1919, but they were expelled by Denikin's forces.With Denikin's defeat and the Ukrainians in severe trouble, they made an alliance with the Poles in April 1920, the combined Polish-Ukrainian forces pushed back the Reds, who occupied most of Ukraine.This was part of the Polish–Soviet War, and ended up with gains for Poland after the treaty of Riga in 1921, but with nothing for the Ukrainians who were fully defeated.