Clear communications were critical to the success of the Allies in World War II. The stability of the Allied transmitters and receivers depended on the performance of tiny quartz crystals. During WWII, the heavy reliance on these crystals spurred on tremendous advances in the manufacturing of dependable products. Before the wartime need, the performance of radio crystals was largely inconsistent. There was little need for wireless communications of the wartime magnitude. After all, wired radios and telephones were used in World War I. But the tactical needs of WWII essentially created the crystal resonator/oscillator industry beginning in Carlisle, PA.
Crystal Clear: The Struggle for Reliable Communications Technology in World War II by Richard J. Thompson, Jr. (Wiley-IEEE Press, October 2006, ISBN: 0-470-04606-6, www.wiley.com) is an excellent text on the early years of the crystal-oscillator industry. After the Manhattan Project, the advances in crystal-oscillator manufacturing represented the second-largest scientific undertaking of WWII. The book details the efforts of dedicated scientists from the Office of the Chief Signal Officer of the US Army, amateur radio operators ("hams") working with crystals, and creative individuals like Karl Van Dyke and F. Dawson Bliley. In doing so, it illustrates how they refined a once-primitive technology in support of the Allied success.