he Scramble for Africa: White Man's Conquest of the Dark Continent from 1876 to 1912 by Thomas Pakenham. (See my first and second posts on the book.)
Specifically, I have been reading about the German war against tribes in German South West Africa in the first decade of the 20th century. An estimated 100,000 members of the tribes revolted against the Germans, pushed too far by a regime of murder, rape and forced labor by the settlers. Troops from Germany, under "extermination orders" attacked the tribes, drove them into deserts, blocked reentry and told them to cross the deserts to other countries. Of course, tribe members realized that was impossible. The Germans eventually took the remaining survivors of the tribes into concentration camps, An estimated 20,000 survived the policy.
In the first decade of the 20th century, there was also a revolt against the Germans in their East African colony (Tanzania), apparently due to forced labor demands that were so high as to prevent tribal members from working their fields enough to feed themselves and their families. The Germans decided that famine was a more practical means to put down the revolt tham military action, especially since the German military were already involved executing the "extermination order" in West Africa. So crops were burned to deliberately create a famine. It is estimated that a quarter million to 300,000 people died -- half of one tribe, more than half of another, and 3/4th of a third tribe that had participated in the revolt.
There were less numerically significant atrocities that also should have alerted the world to the perils of German governance. For example, a lieutenant sent to negotiate a treaty with a native village, instead had his men shoot all the men and women in the village and the 54 children that had survived were put in a basket and drowned.
Yesterday I heard a book talk on TV by Diana Preston about her book A Higher Form of Killing: Six Weeks in World War I That Forever Changed the Nature of Warfare. Preston said that the German strategy in World War I had been based on the belief that Germany could quickly win the war on the Western Front, before the British, French and Russian Empires could fully mobilize their forces (and while the United States remained neutral). She said that when the Western Front quickly stabilized, the German political leadership and high command looked for ways to advance the war more quickly.
Rules of war had been promulgated in the previous decade prohibiting the use of poison gas as a weapon of war and prohibiting the bombing of civilian populations in the cities of an enemy nation. A long standing rule had been that a war ship might stop a commercial ship serving the enemy and inspect it for contraband (e.g. weapons or munitions); if such were found, the ship could be sunk, but only after civilian passengers and crew were allowed to escape. In six weeks of 1915 the Germans broke all three rules, using chlorine gas against Canadian and French troops on the Western Front, bombing London (using zeppelins to deliver the bombs) and sinking the Lusitania by an unanounced attack by a submarine which killed more than 1100 passengers and crew.
This history adds helps one to evaluate the Holocaust created by Nazi Germany in World War II.