If you ask the average Briton, he will tell you that Robert Watson-Watt invented radar in 1935. A German, asked the same question, would reply Christian Hulsmeyer in 1904. Strictly speaking, neither reply would be correct. It is generally accepted that the acronym RADAR stands for “Radio Direction and Ranging”, thus a practical radar system requires that both direction and range be determined. For this, the development of high power pulse transmission, and techniques for direction finding and timing of very short time intervals were needed. Over a period of years, these were individually developed for other purposes, but radar arrived only when all were combined into a single system. By 1939 radar development was also proceeding in a number of countries including France, Holland, Russia and the USA, but only the United Kingdom and Germany had brought it to an operational state.