Originally published in 1954, as a second edition of a 1947 original, this book explores in depth the rapid research and development of radar technology throughout the Second World War. Notably, the subject matter of radar falls into two distinct categories: the principles of the subject and their application to practical use. The principles are described in the first sixteen chapters of the book, whilst the last three chapters deal with the practical application of radar. The book also presents a description of military radar, the civil uses of radar and the extensive applications of radar technique in the physical sciences. Diagrams and photographs are included for reference. This book will be of great value to scholars of the history of physics.