By 1943, many Danes were involved in underground activities, ranging from producing illegal publications to spying and sabotage. Major groups included the communist BOPA (Danish: "Borgerlige Partisaner", Civil Partisans) and Holger Danske, both based in Copenhagen. Resistance agents killed an estimated 400 Danish Nazis, informers and collaborators until 1944. After that date, they also killed some German nationals.