TheCodeBreakers
Russian armies in combat and sent a corps to turn the Russian left
flank. He hoped to effect another Tannenberg—a double envelopment. In
sharp fighting around Lodz, the German forces drove their enemy back,
abetted by a constant stream of cryptanalyzed intelligence. On November
15, for example, the German command learned that four corps were to
reinforce Russian troops at the Ner and Bzura rivers and that another
corps was to cross to the left bank of the Vistula at Plozk. These details
enabled the Germans to maneuver each day as if in a war game.
By now the Russians were changing the key to the order of the cipher
alphabets—not the alphabets themselves— each day. The cryptanalysts
kept pace. On November 18, it appeared that the Germans had won their
victory when the cryptanalysts solved a message ordering a Russian
retreat from Lodz. But the rejoicing at headquarters was cut short when
the codebreakers read a message from Grand Duke Nicholas
annaabi.ee 
