Liza Mundy, Hachette, 416 pages, $28. In the past few years, forgotten women of science at the Harvard Observatory and the black mathematicians at NASA have been rescued and celebrated. Now it is the turn for women recruited by the Army and the Navy during World War II and trained in secret programs to break Japanese and German military codes. For “Code Girls,” journalist Liza Mundy skillfully interweaves the history of the war and the evolution of modern military intelligence with the daily lives of the women who were racing to decipher the messages of the enemy, while dealing with bureaucratic rivalries, administrative sexism, romance and heartbreak on the home front. In 1942, only about 4 percent of American women had graduated from a four-year college. The elite Seven Sisters colleges had their finest hour as the Navy used their top students in mathematics, science and languages. The recruits ran early computers, built libraries, translated documents and formed teams to solve the elaborate, ever-changing codes of the Japanese navy. Not everything was triumphant. A cohort of code girls was still seen by some military administrators as extra secretaries, cute mascots or natural drudges. And after the war, women were expected to give up their jobs. A few code girls went on to high positions at the National Security Agency, but as a cohort, their postwar job opportunities and their chances for further education under the GI Bill were mixed at best. We owe Mundy gratitude for rescuing these hidden figures from obscurity.