Unbreakable: The Spies Who Cracked the Nazis’ Secret Code

Gr 5-8–Deciphering the infamous German military code—helping to end the Second World War—began with the mistaken delivery of an early Enigma code machine to a Polish customs office in 1929. But the focus here is mostly on the heroic work done in the 1930s and 1940s by Polish, French, and British spies and mathematicians, around the clock and under tremendous, often life-threatening, pressure. Some readers will be familiar with computing pioneer Alan Turing and his significant work on the codebreaking project at England’s Bletchley Park. But Barone brings much deserved attention to some fascinating figures not often celebrated in popular histories, from Hans Thilo-Schmidt, a German spy and brother of a prominent military officer who secretly shared intelligence with French counterparts for years; to the Polish electronics expert Antoni Palluth, who worked to reverse-engineer the Enigma machine; and British undergraduate Harry Hinsley, whose behavioral insights and math wizardry helped the team at Bletchley Park find new ways of thinking about the code. A showdown between a Gestapo officer and Palluth’s wife, Jadwiga, is particularly harrowing. Historical photos highlight important figures and war machinery throughout the text, though the mostly unbroken layout will appeal more to stronger readers. The volume concludes with an annotated time line, extensive bibliography, and a dozen pages of meticulous source notes.