The book, entirely written on archival materials, is dedicated to one of the little-known pages of the Great Patriotic War - the Vyazemsky offensive operation, carried out in January-April 1942. This was the time when Soviet troops first encountered a system of well-fortified enemy strongholds. The reader will find out at what cost the German defense broke through, why our troops suffered such heavy losses during the offensive and why its results were so modest. How they learned to take German strongholds, how the first assault detachments were created and how new victorious tactics were born in fierce battles, forcing the enemy to abandon focal defense forever. For the first time, the book tells about many tragic and heroic events, while unknown to the general reader, unique documents, photographs and letters from the front are published.