A few months ago I was asked to deliver a lecture to the Royal United Services Institution on the Radio War. In the preamble to that lecture I explained that my treatment of the subject would not consist of a description of the various radio devices which were used in the late war for purposes of communication, early warning and air navigation, but rather of a treatise on the methods that were employed to deny to our enemies the use of their radio services. My lecture dealt mainly, therefore, with the use of radio as a weapon; and the tactics that we evolved to exploit its employment for such a purpose not only in the defence of this country, but also in the protection of our bomber forces when attacking targets in enemy territory.