The Seljuk Turks.
buyids
Mongols
The British captured Baghdad in 1917 right before the end of WWI There is on the net a very illuminating letter from Lawrence of Arabia, written to the Times if my memory serves, written in 1921. It compares to the situation there as we speak !
Baghdad is Baghdad, there is no former name for the city, nor Persepolis or Babylon.
when the invading Mongol armies captured the Abbasid capital of Baghdad.
1258
The Seljuk Turks.
Hülegü Khan of the Mongols conquered Baghdad in 1258, effectively ending the Abbassid Caliphate.
When Halagu Khan, the Mongol general sacked Baghdad.
The Buyids captured Baghdad in 945CE
buyids
Many of the Mongols converted to Islam. They intermarried with the local people. Over time, the Mongols rebuilt the cities they destroyed during the invasion. In order to capture Baghdad, the Mongols laid a brutal siege upon the city in 1258. Additionally, the Mongols as a political force were expelled from Baghdad in 1341. The Mongols as an ethnic group were never a large population, this meant that after the fall of the Mongol political unit that they were quickly overcome by intermarriage and disappeared ethnically after the mid-1400s.
Baghdad
Hulagu Khan of the Mongols defeated Abbasid Caliph Al-Musta'sim in 1258 in Baghdad. He completely conquered the Abbassid Empire and made sure to raze every city to the ground that gave him one iota of resistance.
The burning of Baghdad effectively ended the Abbassid Empire and confirmed what most Muslims had already suspected for generations, which was that the idea of a unified Islamic World would remain an object of the past.
There are quite a number of Arab Empires. Assuming you are referring to the Abbassid Caliphate, that was destroyed in 1258, when the Mongols led by Hulegu Khan razed Baghdad to the ground.