One of the least known chapters of World War II, Operation Mars, ended in a failure of truly colossal proportions. The operation, which aimed to dislodge the German army from its bridgehead west of Moscow, cost the Soviet Union approximately 335,000 killed, missing and wounded and more than 1,600 tanks. However, the battle is not mentioned at all in Soviet literature: the historical defeat was hidden by post-war Stalinist censorship. In this book, David Glantz provides the first detailed account of its kind on the forgotten disaster, listing the main troops and detailing the events of Operation Mars. Using materials from German and Russian archives, he recreates the historical context of the operation, showing it both from the point of view of the Supreme High Command and through the eyes of ordinary participants. Lasting three terrible weeks, Operation Mars became one of the most tragic pages of Soviet military history. Glanz's reconstruction of the events of this failed offensive fills a serious gap in our knowledge of the Second World War and at the same time raises questions about the reputation of recognized national heroes.