Kozlov. Crimean Tatars and Nogai Tatars traditionally used the sparsely inhabited area of the Wild Fields on the south border of Russia immediately south of Severia to launch annual raids into the Russian territories along the Muravsky Trail and Izyum Trail. In 1591, a Tatar raid reached the Moscow region, forcing the Russian government to build new forts of Belgorod and Oskol in 1593, Yelets in 1592, Kromy in 1595, Kursk in 1597, Tsarev-Borisov and Valuyki in 1600. Tsarev-Borisov, named after Tsar Boris I, was the oldest settlement in Sloboda Ukraine. During those raids regions near Ryazan and along Oka River suffered the most. With the Russian territorial expansion south and east into the lands of modern Sloboda Ukraine and mid-Volga River the conflict intensified. Sometime between 1580s and 1640s the Belgorod Defense Line with number of fortifications, moats, and forts was constructed in Sloboda Ukraine, providing security to the region. After a number of Russo-Crimean Wars, the Russian monarchs started to encourage the settlement of the region by Cossacks who acted as a sort of frontier guard force against the raids of the Tatars. Apart from the Cossacks, the settlers included peasants and townspeople from Right and Left-bank Ukraine, divided by the Treaty of Andrusovo in 1667. The name Sloboda Ukraine derives from the word sloboda, a Slavic term meaning "freedom" (or "liberty)", and also the name of a type of settlement. The Tsar would free the settlers of a sloboda from the obligation of paying taxes and fees for a certain period of time, which proved very enticing for settlers. By the end of the 18th century, settlers occupied 523 slobodas (slobody) in Sloboda Ukraine. From 1650 to 1765, the territory referred to as Sloboda Ukraine became increasingly organized according to Cossack military custom, similar to that of the Zaporozhian Host and Don Host. The relocated cossacks became known as Sloboda Cossacks. There were five regimental districts (polky) of Sloboda Cossacks, named after the towns of their sustained deployment, and subdivided into company districts (sotni). Regional centers included Ostrogozhsk, Kharkiv, Okhtyrka, Sumy, and Izyum, while the Sloboda Ukraine Cossack capital was located in Sumy until 1743. The administration of Catherine the Great disbanded the regiments of Slobozhanshchina and abolished Cossack privileges by the decree of July 28, 1765. The semiautonomous region became a province called Sloboda Ukraine Governorate (Slobodsko-Ukrainskaya guberniya). Saint Petersburg replaced the regimental administrations with Russian