In War Before Civilization , Lawrence H. Keeley, a professor at the University of Illinois, says that approximately 90–95% of known societies throughout history engaged in at least occasional warfare, and many fought constantly.
Despite the undeniable carnage and effectiveness of modern warfare, the evidence shows that tribal warfare is on average 20 times more deadly than 20th century warfare. At one battle lost in 1857 among the Mohave-Yumas, 49.6% of combatants were killed; in a great Aztec battle fought in 1478, 87.1% of 24,000 combatants were killed, while 100% of combatants were killed during the Blackfoot Indian raid which annihilated the Assiniboins in 1849.
The financial cost of the World War II is estimated at about a $1.944 trillion U.S. dollars worldwide, making it the most costly war in capital as well as lives.
Property damage in the Soviet Union inflicted by the Axis invasion was estimated to a value of 679 billion rubles. The combined damage consisted of complete or partial destruction of 1,710 cities and towns, 70,000 villages/hamlets, 2,508 church buildings, 31,850 industrial establishments, 40,000 miles of railroad, 4100 railroad stations, 40,000 hospitals, 84,000 schools, and 43,000 public libraries
“ Give me the money that has been spent in war and I will clothe every man, woman, and child in an attire of which kings and queens will be proud. I will build a schoolhouse in every valley over the whole earth. I will crown every hillside with a place of worship consecrated to peace.” -Charles Sumner
Many wars have been accompanied by significant depopulations. During the Thirty Years' War in Europe, for example, the population of the German states was reduced by about 30%.The Swedish armies alone may have destroyed up to 2,000 castles, 18,000 villages and 1,500 towns in Germany, one-third of all German towns.