in western Caucasus. The major gap in the western section of the line of defense was solved in 1792 when the Black Sea Cossacks were re-settled there. The next three decades brought severe difficulties for the Russian effort in the Caucasus. After the joining of Georgia to Russia in 1801 and the subsequent Russo-Persian War (1804–1813), the Terek Cossacks spared some men and took part in combat under Yerevan, but on the whole most of them were in constant defence of their home lines. All this changed when in 1816 General Yermolov took command of the Caucasus army. Having by now secured major strategic footholds in most of the North Caucasus and Georgia following the last war fought with Persia and the resulting Treaty of Gulistan, he found himself able to make major adjustments. In 1818 he changed the Russian tactics from defensive to offensive and began building the Sunzha-Vladikavkaz line where strongholds such as Groznaya and Vnezapnaya were founded. Yermolov further reformed the whole structure of the Cossacks and in 1819 replaced elected Atamans with appointed commanders. In Transcaucasia, Cossacks took part in the Russo-Turkish War (1828–1829) where they participated in the Siege of Kars and other key battles. After Yermolov was recalled from the Caucasus, a new reform took place and the interim regiments in the central Caucasus were united with the three Hosts on the Terek to form the Caucasus Line Cossack Host (Кавказское линейное казачье войско, Kavkazskoye lineynoye kazachye voysko) in 1832, and the new Nakazny Ataman was named Peter Verzilin. Several reforms followed: In 1836 the Kizlyar and Family regiments were united and made responsible for the Terek Delta, and in 1837 a Malorossiyan (Little Russian) regiment (formed in 1831 to combat the November Uprising in Poland) was resettled on the upper Terek north of Vladikavkaz. In 1842 the regiment was incorporated into the Line host. This was followed by the formation of the Sunzha regiment with its Ataman Sleptsov. By this point the Russian control in the Caucasus had improved, with the initiative firmly in the Cossack hands. Most of the battles took place in Chechen and Dagestani territories far away from Cossack homes. During the 1840s several successful expeditions were mounted deep into the mountains. The Line Cossacks participated in the Crimean War (1853–1856) and finally in the closing phase of the Russian advance against Shamil in 1859. Terek Cossack Host 1860–1920s The