Okay kiddo, so a long, long time ago, there was a group of people called the Mongols who lived in a place called Mongolia. They had super good warriors and were really good at fighting.
One day, the leader of the Mongols, a man named Genghis Khan, wanted to expand their empire and conquer more land. So, they started to travel around and fight other places to take them over.
One of the places they wanted to take over was the Khwarazmian Empire, which was a big area that included parts of what we now call Iran, Turkmenistan, and Uzbekistan.
But, the leader of the Khwarazmian Empire wasn't too happy about this. His name was Shah Muhammad and he didn't want to give up his power to the Mongols. So, he killed some Mongol messengers who came to talk to him, which made Genghis Khan really mad.
Because of this, the Mongols invaded the Khwarazmian Empire with their big army and lots of weapons. They were very good at fighting and so they quickly took over most of the area.
The Mongols did a lot of damage during the invasion. They burned down cities, killed lots of people, and looted whatever they could find. It was a very bad time for the people living in the Khwarazmian Empire.
Eventually, the Mongols took over the whole empire and it became a part of their big empire. But, the invasion caused a lot of destruction and it took a long time for the people in the area to recover.