Rubuta ci gaba don wannan sakin layi - Kamar yadda waɗannan rikice-rikicen kan iyaka suka kasance masu ban tsoro, Yakin Poland-Soviet na 1919<unk>1921 shine mafi mahimmancin jerin ayyukan soja na zamanin. Piłsudski ya nishadantar da zane-zane na hadin gwiwar Rasha a Gabashin Turai, kuma a 1919 sojojin Poland sun tura gabas zuwa Lithuania, Belarus da Ukraine ta hanyar amfani da damuwar Rasha game da yakin basasa, amma ba da daɗewa ba suka fuskanci hare-haren Soviet na yammacin 1918-1919. Yammacin Ukraine ya riga ya kasance wasan kwaikwayo na Yakin Poland-Ukraine, wanda ya kawar da Jamhuriyar Jama'ar Yammacin Ukraine da aka ayyana a watan Yulin 1919. A cikin kaka na 1919, Piłsudski ya ƙi buƙatun gaggawa daga tsoffin ikon Entente don tallafawa motsi na White na Anton Denikin a cikin ci gaban Moscow. Yakin Poland-Soviet da ya dace ya fara ne da hare-haren Kiev na Poland a watan Afrilu na 1920. A hade tare da Daraktan Ukraine na Jamhuriyar Jama'ar Ukraine, sojojin Poland sun ci gaba da wuce Vilnius, Minsk da Kiev a watan Yuni. A wannan lokacin, wani babban Soviet counter-offensive tura Poles daga mafi yawan Ukraine. A gefen arewa, sojojin Soviet sun isa gefen Warsaw a farkon watan Agusta. Nasarar Soviet da saurin ƙarshen Poland kamar ba makawa. Koyaya, 'yan Poland sun sami nasara mai ban mamaki a Yaƙin Warsaw (1920). Bayan haka, ƙarin nasarorin soja na Poland
bi, da kuma Soviets ya janye baya. Sun bar yankuna da yawancin mutanen Belarus ko Ukrainians ke zaune a ƙarƙashin mulkin Poland. An kammala sabon iyakar gabas ta hanyar Zaman Lafiya na Riga a watan Maris na 1921.