This collection of articles, originally published in the Signal Corps Bulletin between 1925 and 1942, offers a glimpse into the evolving world of cryptography and cryptanalysis during the early 20th century. It primarily focuses on the experiences of World War I, showcasing both the successes and failures of code-making and code-breaking efforts. The authors, primarily military signal officers, emphasize the practical realities of using codes in the field, highlighting the dangers of carelessness and the need for well-trained personnel. The work is notable for its historical perspective, offering valuable insights into the development of cryptographic techniques, the evolution of codes and ciphers in response to wartime demands, and the emergence of cryptanalysis as a vital tool for military intelligence. However, the book is limited by its focus on military applications and its occasional tendency to romanticize the role of cryptography. Nevertheless, it provides a fascinating account of the early stages of modern cryptography and its impact on warfare. Body is facsimile edition from best available scan of 1942 US publication declassified by National Security Agency in 1959. Odd/even pages were offset, have been moved inwards and rebalanced. With a bookplate from the home of William F. Friedman.