Racism was the main target of Du Bois's polemics, and he strongly protested against lynching, Jim Crow laws, and discrimination in education and employment. His cause included people of color everywhere, particularly Africans and Asians in their struggles against colonialism and imperialism. He was a proponent of Pan-Africanism and helped organize several Pan-African Congresses to free African colonies from European powers. Du Bois made several trips to Europe, Africa and Asia. After World War I, he surveyed the experiences of American black soldiers in France and documented widespread bigotry in the United States military.