Lisa L. Owens - World War II Code Breakers

Lisa L. Owens

Lerner Publications Minneapolis

Content consultant: Eric Juhnke, Professor of History, Briar Cliff University

Copyright 2019 by Lerner Publishing Group, Inc.

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Library of Congress Cataloging-in-Publication Data

The Cataloging-in-Publication Data for World War II Code Breakers is on file at the Library of Congress.

ISBN 978-1-5415-2151-3 (lib. bdg.)

ISBN 978-1-5415-2155-1 (eb pdf)

Manufactured in the United States of America

1-44380-34645-2/21/2018

Contents

Introduction

Introduction Enigma

In July 1939, Polish mathematician Marian Rejewski and several British, French, and Polish code breakers held a secret meeting in the woods outside Pyry, Poland. In the meeting, Rejewski passed information to the British and French about a machine the German military used to send coded messages. The machine was called Enigma.

Two German operators work with an Enigma machine in June 1940.

German engineer Arthur Scherbius had invented the first version of Enigma in 1918, near the end of World War I (19141918). The machine had a keyboard, rotor wheels, and several wires. The machine operator would reset the wires and wheels each day. When the operator pressed a key to type a message, the rotor wheels turned, causing a different letter to light up on the display. This letter was placed in the coded message. A second Enigma machine with the same settings could decode the message. The rotors made the coded messages seem random, so the code was difficult to break.

Rejewski had been working since 1932 to figure out Enigma. He created a machine called Bomba that could quickly decode messages from Enigma. By 1938 Rejewskis team could decode about percent of German coded messages. But then the Germans changed the machine to make their messages even harder to decode.

At first, Rejewski could only work on Enigma alone and at night to keep his work secret from other workers at his organization. Later, others joined him to crack the German codes.

Rejewski shared what he knew with the French and British code breakers. Just five weeks later, Germany invaded Poland to begin World War II (19391945). Decoding secret military messages suddenly took on new importance. The French and British, members of the Allied forces fighting against Germany and the other members of the Axis powers , were determined to break the Enigma code.

STEM Highlight

A code or cipher is used to produce hidden messages. In a code or cipher, letters or words are changed to other letters, words, numbers, or symbols. The person receiving the coded message must know how the code works to translate the message. Code breakers often do not know what kind of code they are reading, so they must look for patterns and repeated words or letters to figure out the code.

Chapter Bletchley Park

When World War II began, about code breakers in Britain moved to a mansion in Buckinghamshire, England. The mansion, known as Bletchley Park, was Britains code-breaking headquarters. There, mathematicians, engineers, scientists, and others skilled at solving puzzles and working with languages worked to intercept , decode, and interpret messages from Germany, Italy, and Japan.

By the end of the war, nearly ten thousand code breakers worked at Bletchley Park.

Top Secret

The work done at Bletchley Park was highly secretive. In fact, nobody else knew that the code-breaking headquarters existed until the 1970s, about thirty years after World War II ended. Even the code breakers