In view of the very wide scope of Operational Research in both the civil and defence fields, it is instructive to recall that it originated in wartime, as a means of increasing the operational effectiveness of combat forces. In the Second World War in particular it had a major effect on the efficient functional uses of the new radar equipment and achieved many other notable successes in increasing the effectiveness of our forces. It rapidly spread to all Services and in particular it was introduced into the Army through the formation in 1941 of the Army Operational Research Group, which in 1961 became the Army Operational Research Establishment, which in turn became in 1965 the tri-Service Defence Operational Analysis Establishment. Operational Research in wartime, functions in direct contact with the operational environment and the analytical predictions which it makes leads to direct application to the real world of war, the outcome in many cases being checked against the predictions. Operational Research in the original sense of investigation of operational factors continues to play a major part in peacetime in increasing the potential effectiveness of the services.