After failing to capture Kiev on their own, the Ukrainian army signed the Treaty of Warsaw with Poland, in April 1920. Under the treaty, Ukrainian forces fought side by side with Polish forces against Soviet Russia and other Ukrainian 'Red' movements (Denikin, the Germans and the Entente had long since been expelled from Ukraine). Following a decisive failure in the Kiev Offensive, Ukrainian presence only decreased in the seesaw Polish-Soviet war. Until finally the newly founded Soviet Union and Poland signed the Treaty of Riga on March 18, 1921, ending the war. The small remnants of the Ukrainian People's army either resorted to Guerrilla warfare or joined the Polish Army.