Simplify the following text for a Grade 11 native English-speaking person.
Original: Under Hulagu 's leadership , the Mongols destroyed the greatest center of Islamic power , Baghdad , and also weakened Damascus , causing a shift of Islamic influence to the Mamluks in Cairo .
Simplified: Under his leadership , the Mongols destroyed the two greatest centers of Islamic power , Baghdad and Damascus , causing a shift of Islamic influence to the Mamluks in Cairo .