For decades, the UK's Joint Intelligence Bureau tracked the Soviet Union's nuclear expansion through a Belgian transit company, hiding the true scale of the Bloc's industrial power.
North Korea’s bid for nuclear power and massive arms shipments met a hard line from Moscow as the client state failed to pay substantial export arrears.
Czechoslovakia and East Germany blocked students from accessing state secrets in nuclear physics after Pyongyang urgently offered to pay all costs for 95 trainees.