Of what is listed Germany lost the highest percentage of its population. Their numbers, though, were no where near the percentages of what was lost by the USSR. More men were lost there. Russia actually had both men, women, and children fighting in the war. This allowed for a greater chance of more loss of life.
The Mongol Empire, with its peak size under the rule of Kublai Khan around the year of 1279, included parts of modern Russia in the North, modern day Korea, and modern China in the South on one end of the Asian continent. It stretched through the Asian continent all the way to modern day Hungary in Europe. It also included parts of the modern Middle East such as Iraq and Iran. The total area of the Mongol Empire in its peak was around 40 million km^2.
civil wars and lots of invasion
