A Mongol army commanded by Tolui captured the city of Merv in present-day Turkmenistan, allegedly killing more than 1.7 million people.

The Mongol Empire was the largest contiguous empire in history. Originating in present-day Mongolia in East Asia, the empire at its height stretched from the Sea of Japan to Eastern Europe, extending northward into the Arctic; east and southward into the Indian subcontinent, mounting invasions of Southeast Asia, and conquering the Iranian plateau; and reaching westward as far as the Levant and the Carpathian Mountains.

Tolui was the youngest son of Genghis Khan and Börte. A prominent general during the early Mongol conquests, Tolui was a leading candidate to succeed his father after his death in 1227 and ultimately served as regent of the Mongol Empire until the accession of his brother Ögedei two years later. Tolui's wife was Sorghaghtani Beki; their sons included Möngke and Kublai, the fourth and fifth khans of the empire, and Hulagu, the founder of the Ilkhanate.

Merv, also known as the Merve Oasis, was a major Iranian city in Central Asia, on the historical Silk Road, near today's Mary, Turkmenistan. Human settlements on the site of Merv existed from the 3rd millennium BC until the 18th century AD. It changed hands repeatedly throughout history. Under the Achaemenid Empire, it was the center of the satrapy of Margiana. It was subsequently ruled by Hellenistic Kings, Parthians, Sasanians, Arabs, Ghaznavids, Seljuqs, Khwarazmians and Timurids, among others.

Turkmenistan is a landlocked country in Central Asia, bordered by Kazakhstan to the northwest, Uzbekistan to the north, east and northeast, Afghanistan to the southeast, Iran to the south and southwest, and the Caspian Sea to the west. It is one of six independent Turkic states. Ashgabat is the capital and largest city. With over 7 million people, Turkmenistan is the 35th most-populous country in Asia and has the lowest population of the Central Asian republics while being one of the most sparsely populated nations on the Asian continent.