He was considered one of the main ideologists of Tito's communist regime in former Yugoslavia. He had major influence on the Yugoslav military intelligence service, the KOS. He advocated the hiring of convicts into the service, who were used to assassinate many Yugoslav political exiles. In exchange for their services, convicts were given safe haven in the country, protected even from Interpol. Many of these people were alleged to have robbed banks, and carried on other criminal activities all over Western Europe. The notorious Arkan (Željko Ražnjatović), is said to have begun as Kardelj's protege.

He also led Yugoslav delegations in the late 1940s to negotiate with Stalin and deal with his demands that Yugoslavia acknowledge the Soviet Union's supremacy.

Some above statements should be NPOVed'.