The cryptanalysts working for the Signals Intelligence Service (SIS) of the U.S. Army knew how crucial it was to decipher and read Japanese secret messages. But this new code, "Purple," wasn't breaking. For eighteen months the team struggled with this difficult Japanese diplomatic code. Then, one day in September 1940, Genevieve Grotjan made a discovery that would change the course of history. By analyzing and studying the intercepted coded messages, she found a correlation that no one else had yet detected. This breakthrough enabled other cryptanalysts to find similar links. Shortly thereafter, SIS, long with the U.S. Navy, built a "Purple" analog machine to decode the Japanese diplomatic messages. Genevieve Grotjan's contribution to the Allied victory cannot be measured. Nor can the contributions of the thousands of women serving their country through the field of cryptography. Like Genevieve, many women working in cryptology during World War II were civilians, thousands of others were in the military. Women who joined the military relieved men working in noncombat positions. These men were desperately needed to fight the battles oversees.