How was Islam able to cross

Islam entered on the Russian scene via Iran in the 7th century A. D. (1st century A. H.). In 642, Azerbaijan came under Muslim control. The Muslims also occupied the extreme border town of Darbund in 658. After the conquest of eastern Caucasia (Qafqaz) Islam began to spread in these areas without any resistance. The Muslim armies crossed the river Oxus in 673. Bukhara fell to the Muslims in 674.