Final answer:
The end of the Byzantine Empire was brought about by the forces of Ottoman Sultan Mehmed II, who captured Constantinople in 1453, leading to its transformation into an Islamic state.
Step-by-step explanation:
The army that brought about the end of the Byzantine Empire by sacking Constantinople was led by Ottoman Sultan Mehmed II, also known as Mehmed the Conqueror. In 1453, Mehmed II marshaled his forces, including Muslim and Christian vassals from various regions, and an elite corps of soldiers. He made use of advanced siege technology, including large cannons crafted by European gunsmiths, to breach the formidable walls of Constantinople that had protected it since the fifth century. The capture of Constantinople signified the fall of the Byzantine Empire and marked the transformation of the former Christian bastion into an Islamic stronghold, with the iconic Hagia Sophia being converted into a mosque.