Kammala wannan jumla: Yayin da Yakin Poland da Soviet ya yi tsanani, a ƙarshen Afrilu 1920 Red Army na sabon gwamnatin Soviet ta Rasha ta tura sojojin Poland baya kuma ta mamaye Poland. Daga baya, Sikorski ya sami nasarar kare Mozyr da Kalenkowicze har zuwa 29 ga Yuni, amma daga baya ya kasa riƙe sansanin Brest, kodayake ya kare shi tsawon lokaci don ba da damar sojojin Poland a yankin su ja da baya cikin tsari. A ranar 6 ga watan Agusta an nada shi kwamandan sabuwar rundunar sojojin Poland ta 5, wanda aka ba shi aikin rike gaba a arewacin Modlin, tsakanin kogin Narew da Wkra. Ya bambanta kansa yana jagorantar rundunar soja ta 5 a gaban Lower Vistula a lokacin yakin Warsaw. A wannan lokacin sojojin Soviet, suna tsammanin nasara mai sauƙi, sun yi mamaki kuma sun gurgunta da hare-haren Poland. A lokacin wannan yaƙin (wani lokacin ana kiransa "Mu'ujiza a Vistula") Sikorski ya dakatar da ci gaban Bolshevik a arewacin Warsaw kuma ya ba Piłsudski, babban kwamandan Poland, lokacin da yake buƙata don adawa da shi; farawa da 15 Agusta sojojinsa sun yi nasarar shiga cikin Sojojin Soviet na 5 da na 15. Bayan yakin Warsaw, daga 30 ga Agusta, Sikorski ya umurci rundunar soja ta 3. Sojojinsa sun ɗauki Pińsk, kuma sun yi yaƙi a ƙarshen matakan Yaƙin Lwów da Yaƙin Zamość, sannan bayan
Yaƙin Niemen ya ci gaba da sojojinsa zuwa Latvia da zurfin cikin Belarus. Yaren mutanen Poland sun kayar da Soviets, kuma Yarjejeniyar Riga ta Poland-Soviet (Maris 1921) ta ba Poland manyan yankuna na Belarus da Ukraine (Kresy). An kara darajar Sikorski yayin da ya zama sananne ga jama'ar Poland a matsayin ɗaya daga cikin jaruman Yakin Poland-Soviet. Ya kuma ci gaba da wallafa labaran kimiyyar soja a lokacin yakin kanta. Saboda nasarorin da ya samu Sikorski ya zama babban janar a ranar 28 ga Fabrairun 1921, kuma an ba shi lambar yabo ta soja mafi girma a Poland, umarnin Virtuti Militari, a ranar 15 ga Maris na wannan shekarar.