"And we took all his cities at that time, and utterly destroyed the men, and the women, and the little ones, of every city, we left none to remain." - Deuteronomy 2:34 (Holy Bible)
In Jewish and Christian mythology the first five books of the Bible are said to have been written by Moses himself. Certainly Moses is a central figure, particularly in the second book, Exodus, in which he leads the Jews out of slavery in Egypt. At the end of the fifth book, Deuteronomy, Moses is said to have died at the age of 120, in Moab, never having entered the land of the Canaanites. Joshua then led the Jewish tribes, conquering the city of Jericho and, afterwards, conquering areas west of the Jordan River and Dead Sea.
It is likely that the Jewish original conquest of what I will call Palestine was not quite as clearly genocidal as the Bible indicates. The above quote from Deuteronomy is ascribed to the period during which the tribes were wanderers, before settling in Palestine. The Jews where not alone in trying to exterminate their neighbors, they just recorded it earlier than most. Enslaving the conquered was another common option, as was killing all males and keeping women as wives and slaves. The Egyptians, Sumerians and Babylonians also boasted of their skills at war and built their grand civilizations with slaves.
Many other instances of genocide are recorded in the Bible. For instance in Samuel, Chapter 15, God himself is quoted as saying: "Now go and smite Amalek, and utterly destroy all that they have, and spare them not; but slay both man and woman, infant and suckling, ox and sheep, camel and ass."
At one point the Babylonians did an ethnic cleansing of Judah, leading to the Exile. Most scholars think most of the Bible was written in Babylonia to keep the Jews culturally united until they could return to Judah. [6th century BCE; see Babylonian captivity]
What makes the Hebrew record different is its pretense to being a display of God's plan for the world. If you accept the Bible as a plan, you are basically stuck with approving of genocide and ethnic cleansing.
Adolf Hitler could well be said to have been the Moses of Germany. He was born in an ethnically German area of the Austro-Hungarian Empire. The most fateful decision of his life was doubtless when he decided to abandon a career as an artist to enroll in the German (rather than Austro-Hungarian Empire) army at the beginning of World War I.
Germany defeated Russia in the war and still had troops in France when it surrendered. Corporal Hitler, like many Germans, went into denial. Instead of accepting that if Germany had fought on its army would have collapsed, the myth of the "stab in the back" was created. In this version of history Communists and Jews (often the same people in Germany) were blamed for the loss of the war. There was some basis for this mistaken view. The Balfour Declaration, which may have induced some German Jews to hope for a British victory in the War. After Kaiser Wilhelm abdicated, the transitional government that negotiated the surrender of Germany was socialist (of the Marxist, internationalist sort, not of the nationalist, Nazi sort).
Germans had some genuine postwar complaints. The United States piled into the war late, tipping the military balance. A just peace was promised in return for an armistice. Instead the British, French and Americans imposed a very punitive peace that essentially destroyed Germany.
For Hitler and his admirers the Promised Land was a Germany consisting of all ethnic German majority areas. For Hitler and the more anti-Semitic National Socialists these lands would also have to be purged of foreign races, including (but not limited to) Jews and Gypsies. The more aggressive version of this doctrine included invading non-German areas, purging them, and colonizing them with Germans. Not unlike the prior colonization of the United States and British Empire.
The German nationalists wandered in their wilderness only slightly more than a decade before gaining power in Germany, or the rump of Germany that had been left by the wolves after World War I. In the late 1930's Hitler's government started taking back, or incorporated for the first time, the ethnic German areas outside the official borders. To be sure, he was happy to seize some areas that were not German, like much of Czechoslovakia. The last (perhaps) piece of German pie Hitler gobbled was western Poland (which was a part of Germany taken away by the peace treaty after World War I). The mighty British Empire, itself built over the centuries by the process of military conquest, ethnic cleansing, and genocide, declared war on Germany soon after Poland was attacked. World War II was on.
Like Moses, Hitler was not to see his promised land. Other nations were not interested in accepting the Jews he wanted expelled, so he killed them in the Holocaust, which is one of the most appalling acts of cold blooded mass murder of non-combatants in modern history.
In the end Germany was dismembered, not reunited. Hitler committed suicide rather than surrendering, echoing Masada, and the concentration camps were liberated before they completed their grizzly task. Later the capitalist West put together its three bites (British, French, and American) of Germany in order to use them as a shield against the Communist Block. Only in 1990 did East Germany reunite with West Germany to form the modern (and might I add, civilized and non-militaristic) nation of Germany.
Since World War II ethnic cleansing, and even genocide, has continued here and there around the world. Nationalism, religious prejudice, and greed are still problems. Yet a new earth has grown up too where many if not most people have a modern, civilized outlook. Civilized nations do not even have the death penalty for criminal acts. In theory no nation is supposed to engage in military aggression, though in reality the U.S. has been the worst offender in the last decade or two.
We need to keep a watch out for leaders who advocate ethnic cleansing, genocide, or war. They need to be stopped before they cause harm. We need, in particular, to respect the rights of indigenous peoples and minorities. The whole world should accept the enlightenment ideal of religious toleration and the brotherhood and sisterhood of the human race.
History books are filled with wars and genocides. This makes us forget that most people have lived in peace most of the time. Most people do not murder their neighbors. Nor do villages or cities exist in a perpetual war with each other. Even mighty nations have spent most of their times in treaty-bound peace with their rivals. We have much to build on even as we remember and criticize the horrors of the past.