ather soon after nuclear fission was discovered in 1938 – when its peaceful application as a terrestrial energy resource became recognized – a world-wide dynamic development was set in motion after World War II for its exploitation, with the result that the principal objectives of fission technology were achieved astoundingly quickly. A characteristic feature of this process was the first Conference on the Peaceful Uses of Atomic Energy held in Geneva in 1955, where information on such fission technology became declassified and was exchanged on a world-wide scale. Another feature of this development, in 1957, was the foundation of the International Atomic Energy Agency IAEA with their headquarters in Vienna, which from its very beginning also became a strong supporter of fusion R&D. Stimulated by these early successes and their spirit of optimism, first concepts for the peaceful use of fusion energy likewise emerged well over fifty years ago, though also classified in their early stages (but fully declassified in 1957 when it became clear that they had no military implications). While at that time some countries already had fusion weapons technology (the hydrogen bomb), the move towards the peaceful use of fusion energy with their huge fuel resources and promising features appeared very attractive and challenging, though extremely difficult and protracted. Two statements from that period make this particularly clear and typify the tension recognized early on between high expectations and the most intractable physical and technical difficulties. The first is from H. J. Bhabha in his opening speech to the first Conference on the Peaceful Uses of Atomic Energy held in Geneva in 1955: “I venture to predict that a method will be found for liberating fusion energy in a controlled manner within the next two decades.”Conversely, in the first general article on the fusion issue published 1956 by a scientist from the USA, R.F. Post wrote: “However, the technical problems to be solved seem great indeed.When made aware of these, some physicists would not hesitate to pronounce the problem impossible of solution”. Despite the latter statement, but well aware of it, a worldwide R&D campaign was initiated with the aim of exploring and developing possible concepts which eventually might lead to a machine (reactor) delivering useful energy from controlled fusion processes. Results from these early years of fusion R&D were reported, among others, at the second Conference on the Peaceful Uses of Atomic Energy held in Geneva in 1958. In retrospect it is surprising – and this has to be acknowledged – that the basics of those concepts, which nowadays are considered to be the most successful and promising, had already been published at that time, albeit of course without all the plasma physics knowledge, techniques and insights needed for test and proper scale demonstration. The aim of controlled fusion is presently to build a reactor in which the fusion reaction is the least difficult one to accomplish on earth: 1D+1T→2He(3.6MeV )+ 0n(14MeV ) in a plasma at a temperature of ~ 150 million K. Initially, however, due to their attractive features concerning neutrons and fuel breeding, the D+D, and over some period even theD+He reactions were considered.