<span>To protect the city of Constantinople attacks <span>by sea.</span></span>
The Mongol Empire under Genghis Khan<span> started the conquest with small-scale raids into Western Xia in 1205 and 1207. By 1279, the Mongol </span>leader Kublai Khan<span>had established the Yuan dynasty in China and crushed the last Song resistance, which marked the onset of all of China under the Mongol Yuan rule.</span>
A. It's exact origin is unknown
The electoral college is a system where 538 electors elect the president and Vice President (:
In modern historiography, polis<span> is normally used to indicate the </span>ancient Greek city-states, like Classical Athens and its contemporaries, and thus is often translated as "city-state<span>".</span>
