The Mongol Empire founded by Chinggis Khan (also known as Genghis Khan in the West) became the largest contiguous empire in history, stretching from the Sea of Japan to the Mediterranean Sea and the Carpathian Mountains. At its peak, more than a million men were under arms and enrolled in the armies of the Khan, or the emperor of the Mongol Empire. The Mongol Khans became determined to conquer the world, and, indeed, with the resources at their disposal there was little reason why they should fail. Eventually, however, their empire collapsed, partially under its own weight. The following is a brief history of the rise of the Mongol Empire and its subsequent expansion across Asia and into Europe, until it fragmented into four smaller yet still powerful kingdoms