Leo IV was a long time ago, even before your great-great-great-great-grandparents were born! He was a man who lived in a country called the Byzantine Empire, which is now known as Turkey. Leo IV was the emperor of the Byzantine Empire from 775 to 780.
The Khazars were a group of people who lived in a region that is now known as Russia. They were known for being fierce warriors and they had their own kingdom. The Khazars and the Byzantine Empire were neighbors, so they often interacted with each other.
Leo IV is sometimes called "Leo the Khazar" because he had a Khazar mother and he was married to a Khazar princess. This means that he had a special relationship with the Khazars and he understood their culture and language.
During Leo IV's reign, there were many battles between the Byzantine Empire and the Khazars. Leo IV was a skilled military leader and he was able to win many of these battles. However, there were also times when the Khazars were able to defeat the Byzantine army.
Overall, Leo IV the Khazar was an important figure in the history of the Byzantine Empire and the Khazars. He was able to form a strong relationship with the Khazars and he was a skilled military leader.