Original sentence: The Ukrainian Insurgent Army (, Ukrayins’ka Povstans’ka Armiya; UPA) was a Ukrainian nationalist paramilitary and later partisan army that engaged in a series of guerrilla conflicts during World War II against Nazi Germany, the Soviet Union, Czechoslovakia, and both Underground and Communist Poland.The army also played a substantial role in ethnic cleansing of the Polish population of Volhynia and East Galicia, as well as subsequent defending the Ukrainian population in Poland from the similar actions, and preventing the deportation of the Ukrainians in southeastern Poland
Edited sentence: The Ukrainian Insurgent Army (, Ukrayins’ka Povstans’ka Armiya; UPA) was a Ukrainian nationalist paramilitary and later partisan army that engaged in a series of guerrilla conflicts during World War II together with  Nazi Germany, against the Soviet Union, Czechoslovakia, and both Underground and Communist Poland.The army also perpetrated ethnic cleansing of the Polish population of Volhynia and East Galicia, as well as subsequently defending the Ukrainian population in Poland from deportations; preventing the deportation of the Ukrainians in southeastern Poland