In 1462, the throne of the principality of Moscow passed to the Great Prince Ivan III, who created the first Russian state. For the next 200 years, Russia struggled to maintain its borders against a series of assaults. This was achieved in part through the development of a network of fortified sites called kremlins and the creation of a series of defensive lines of enormous length. This book examines how these fortifications were developed to respond to ever-changing situations under the command of such charismatic rulers as Ivan the Terrible, through to the military reforms of Peter the Great. It also explores the development of the Kremlin, one of the most famous fortification types in the world.