One of the fundamental, inescapable tenets of war is death. Once you move aside all the discussions of equipment, politics, tactics, causes, etc. that is what you are left with. I thought it might be interesting to share some figures compiled by Professor P.J. Rummel, professor of political science at University of Hawaii:
In the 20th century - 50 million dead from international and civil wars. 170 million citizens were murdered by their own governments.
Total - 220 million killed. Some of the top leaders in organized or systematic murder:
Soviet Union, 1917-1987 62 million
People's Republic of China, 1949-1987 35 million
Nazi Germany, 1933-1945, 21 million Jews, Serbs, Slavs, Poles, Romani, Czechs, Ukrainians, et al and those deemed "physical or mental misfits."
Turkey 1909-1918, 2 million
Cambodia, Khmer Rouge - 2 million
Pakistan - 1.5 million
Yugoslavia under Tito - 1.5 million
Mexico, 1900-1920 1 million
Prior to the 20th century, from the time of Christian Crusades and including events such as slavery of Africans, witch hunts, etc. etc. Professor Rummel calculates 133 million deaths.
Why did the 20th century get so much worse? Two reasons: Centralized power of governments and expanding technology. In the 19th century and earlier, governments were generally smaller, authority dispersed among different towns, provinces, etc.
The local authority, religious leaders, etc. may have held as much or more sway over the local populace than the central government or monarch, who was viewed as an obscure, distant figure. Slow communications and travel kept it that way. Could a Hitler, Stalin or Mao have engineered the murder of millions in previous centuries? Thousands and tens of thousands, yes (such events occurred) but millions, no.
Hitler built upon the unification of German states that developed over the course of time due to Bismarck and others. Had he stepped directly onto the scene in the mid-19th century he would have faced a number of quasi-independent German states that would not have all unified behind him.
The lesson from history: A government where all power is centralized and has extensive technological resources at its disposal is a dangerous government.