Frequently a critic of United States and Soviet foreign policy, he expressed his resistance to imperialist ambitions and authoritarian regimes, including those of Francisco Franco of Spain, Leonid Brezhnev of the Soviet Union, António de Oliveira Salazar of Portugal, Gustáv Husák of Czechoslovakia, and most notably John Vorster and P. W. Botha of South Africa, denouncing apartheid as a "particularly gruesome system". His 1972 condemnation of American bombings in Hanoi, comparing the bombings to a number of historical "crimes" including the bombing of Guernica, the massacres of Oradour-sur-glane, Babi Yar, Katyn, Lidice and Sharpeville and the extermination of Jews and other groups at Treblinka, resulted in a temporary freeze in Sweden–United States relations.