Mongols and Timurids
In 1157, the rule of Seljuks dynasty came to an end in the province of Khorasan. The Turkic rulers of Khiva took control of the area of Turkmenistan, under the title of Khwarezmshahs In 1221, central Asia suffered a disastrous invasion by Mongol warriors who swept across the region from their base in eastern Asia.
Under their commander, Genghis Khan, the Mongols conquered Khwarezm and burned the city of Merv to the ground. The Mongol leader ordered the massacre of Merv's inhabitants as well as the destruction of the province's farms and irrigation works which effectively ended the Iranian dominance in urban areas and agricultural communities of khwarezm. These areas were soon repopulated by the Turkmen who survived the invasion and had retreated northward to the plains of Kazakhstan or westward to the shores of the Caspian Sea.
Small, semi-independent states arose under the rule of the region's tribal chiefs later in 14 century. In the 1370s, Amir Timur (known as Tamerlane in Europe),one of the greatest conquerors in human history, captured Turkmen states once more and established the short lived Timurid Empire, which collapsed after Timur's death in 1405, when Turkmens became independent once again.
Read more about this topic: History Of Turkmenistan