In the 1930s, his sympathies were to the political left. When Poland was attacked in 1939 by Germany, he wrote an important poem encouraging Poles to put away political differences and fight the aggressors. While Poland was attacked by Soviet Union and the whole Eastern Borderlands were occupied by the Soviets, Broniewski found himself in territory occupied by the Russians LwóWest
At first, he published his poems in the newspaper published by the Soviets, but soon he was arrested by People’s Commissariat of Internal Affairs on the trumped-up charges of "hooliganism" and after four months transported to the Lubianka prison in Moscow, where he spent further thirteen months.
After the World World War II, in Poland ruled by the pro-Moscow communist regime, he compromised by writing in 1951 an important politically narrative poem "Słowo o Stalinie" ("A Word about Stalin"). Subsequently, Broniewski became an important political figure and was proclaimed by the authorities as a foremost national poet.
Still, Broniewski managed to obtain a certain degree of independence, and some of his poems from this period certify to his talent. He has been also a talented translator of poetry and prose translating, among others, Dostoyevsky, Yesenin, Mayakovsky and Brecht.
During the last years of his life his health had been ruined by alcohol abuse.
He died in Warsaw.