Original sentence: Although today some of the Kuban Cossacks and their descendents do not consider themselves Ukrainians, their local dialect and folklore preserved the Ukrainian influence and many historians consider their predecessors, the Dnieper Cossacks, as founders of what became a modern Ukrainian nation.It is not clear when the Slavic people started settling in the lower reaches of major rivers such as the Don and the Dnieper.It is unlikely it could have happened before the 13th century, when the Mongol hordes broke the power of the Cumans and other Turkic tribes on that territory
Edited sentence: Although most historians agree that the modern Cossacks pre-date to Slavic peoples that settled the lower reaches of major rivers such as the Don and the Dnieper in the 13th century.Although today the Kuban Cossacks and their descendents do not consider themselves Ukrainians, their local dialect and folklore preserved the Ukrainian influence and many historians consider their predecessors, the Dnieper Cossacks, as founders of what became a modern Ukrainian nation.The Mongol Invasion of Rus however changed all that, and as the remnants of the Kievan Rus collapsed many fled the chaos and settled in the naturally protective landscape of the lower river rapids