What occupiers proved to be the worst for Baghdad?

The worst occupiers for Baghdad were arguably the Mongols in the 13th century, particularly under Hulagu Khan, who sacked the city in 1258. This invasion resulted in massive destruction, loss of life, and the collapse of the Abbasid Caliphate, leading to a significant decline in Baghdad's cultural and economic significance. Additionally, the U.S.-led invasion in 2003 also had devastating consequences, resulting in widespread violence, instability, and a prolonged conflict that severely impacted the city's infrastructure and civilian life.