Complex sentence: A great migration reached the region at the end of the 4th century, when Huns came to the Panonian plains, and in the middle of the 5th century, formed a kingdom between the rivers Danube and Tisza under control of the legendary Attilla.
Split into simpler sentences: A great migration reached the region at the end of the 4th century, when Huns came to the Panonian plains. In the middle of the 5th century, the Huns formed a kingdom between the rivers Danube and Tisza under control of the legendary Attilla.