Governments support research and development (R&D) largely because there is a national need to support certain fields and types of research and there is a need for government to have their own sources of technical information and advice. In the UK, the fulfilment of these needs is met by several establishments. The First World War taught the Defence Services that if they were to keep ahead, or even abreast, of the fighting forces of other countries, they must maintain in peace time special organisations of a scientific or technical nature. As a result, each of the three Services set up experimental establishments staffed largely by professional scientists and engineers on full time permanent appointments. These establishments worked under severe disadvantages during the 1920s and 1930s because of economic crises (and therefore threat of severe reductions) and anti-defence opinion in academic circles.