A relatively large and well‐funded group of investigators did intense research on the electrical properties of silicon and germanium during World War II. Their work completely transformed attitudes toward the physical properties of the pure crystalline forms of the semiconductors: No longer regarded merely as exotic materials, these elements became components of flexibly useful circuit elements that could be manipulated to show various properties by the addition of small amounts of other elements. In this sense, the wartime research laid the groundwork for the invention of the transistor shortly after the war and ultimately the development of the integrated circuit. The work opened up a now age of electronics.