Konstantin S Nossov 
Medieval Russian Fortresses AD 862 1480 [PDF ebook] 

According to Russian legend, in the year AD 862 the Slav tribes of what is now European Russia invited a number of Scandinavian princes to rule over them. However, on the death of these princes, Prince Oleg seized Kiev and united the Northern and Southern Russian territories, building extensive fortifications to protect its borders. The rise of feudalism in the 11th century lead to the development of individual fortified sites and the extended border defenses fell into disrepair. Consequently, Mongol hordes poured over the border introducing the siege warfare techniques of the East, heavily influencing the fortification styles thereafter. Using a wealth of archeological evidence and first-hand sources, Konstantin Nossov charts the history of the medieval Russian fortress from its early beginnings until the 14th century, paying special attention to the development of one of the most iconic fortifications in the world: the Kremlin.