On the northern borders of the Ottoman Empire a defensive line of fortresses stretched from Belgrade in the Balkans to Kars in the Caucasus. This was the line along which all of Turkey’s wars with Russia had been fought since the latter half of the seventeenth century (in 1686–99, 1710–11, 1735–9, 1768–74, 1787–92, 1806–12 and 1828–9). The Crimean War and the later Russo-Turkish war of 1877–8 were no exceptions to the rule. The borderlands defended by these fortresses were religious battlegrounds, the fault-line between Orthodoxy and Islam.
