Emil Julius Klaus Fuchs was a German theoretical physicist and one of the most effective atomic spies of the Soviet Union. He transferred crucial information from the British, American and Canadian ‘Manhattan Project’ to the Soviet Union during the Second World War and thereafter. He was inducted as assistant of Rudolf Peierls in the atomic bomb project of Britain, the ‘Tube Alloys’. There he started spying for the Soviet Union and through Ruth Kuczynski passed on significant project information. He accompanied Rudolf Peierls to New York and worked on the ‘Manhattan Project’ at the ‘Columbia University’. Here in ‘Los Alamos National Laboratory’ he worked at the ‘Theoretical Physics Division’. He was involved in several important theoretical calculations associated with first nuclear weapons and hydrogen bomb. Post war, he served as the head of the ‘Theoretical Physics Division’ in the ‘Atomic Energy Research Establishment’ in Harwell, UK. He was later convicted for his espionage that he confessed and was sentenced to an imprisonment of fourteen years. His British citizenship was terminated. After nine years of confinement he was released and sent to East Germany. He was elected to the central committee of the ‘Socialist Unity Party of Germany’. Later he served the ‘Institute for Nuclear Research in Rossendorf’ as its deputy director. He is the recipient of ‘Order of Karl Marx’, the ‘National Prize of East Germany’ and the ‘Patriotic Order of Merit’.