The government of Germany ordered, organized and condoned a substantial number of war crimes in both World War I and World War II. The most notable of these is the Holocaust in which millions of people were murdered or died from abuse and neglect, 60% of them (approximately 6 million out of 10 million)Jews. However, millions also died as a result of other German actions in those two conflicts. The true number of victims may never be known, since much of the evidence was destroyed by the perpetrators, by burning of bodies, murder of witnesses and destruction of documentation in an attempt to conceal the crimes.
In total, from 24,000 up to 100,000 Herero and 10,000 Nama died. The genocide was characterized by widespread death by starvation and thirst because the Herero who fled the violence were prevented from returning from the Namib Desert. Some sources also claim that the German colonial army systematically poisoned desert wells.
In August 1914, as part of the Schlieffen Plan, the German Army invaded and occupied the neutral nation of Belgium without explicit warning, which violated a treaty of 1839 that the German chancellor dismissed as a "scrap of paper" and the 1907 Hague Convention on Opening of Hostilities. Within the first two months of the war, the German occupiers terrorized the Belgians, killing thousands of civilians and looting and burning scores of towns, including Leuven, which housed the country's preeminent university, mainly in fear of Belgian resistance fighters, or francs-tireurs. This action was in violation of the 1907 Hague Convention on Land Warfare provisions that prohibited collective punishment on civilians and looting and destruction of civilian property in occupied territories.
The raid on Scarborough, Hartlepool and Whitby, which took place on December 16, 1914, was an attack by the Imperial German Navy on the British seaport towns of Scarborough, Hartlepool, West Hartlepool, and Whitby. The attack resulted in 137 fatalities and 592 casualties. The raid was in violation of the ninth section of the 1907 Hague Convention which prohibited naval bombardments of undefended towns without warning, because only Hartlepool was protected by shore batteries. Germany was a signatory of the 1907 Hague Convention. Another attack followed on 26 April 1916 on the coastal towns of Yarmouth and Lowestoft but both were important naval bases and defended by shore batteries.
Unrestricted submarine warfare was instituted in 1915 in response to the British blockade of Germany in the North Sea. Prize rules, which were codified under the 1907 Hague Convention—such as those that required commerce raiders to warn their targets and allow time for the crew to board lifeboats—were disregarded and commercial vessels were sunk regardless of nationality, cargo, or destination. Following the sinking of the RMS Lusitania on 7 May 1915 and subsequent public outcry in various neutral countries, including the United States, the practice was withdrawn. However, Germany resumed the practice on 1 February 1917 and declared that all merchant ships regardless of nationalities would be sunk without warning. This outraged the U.S. public, prompting the U.S. to break diplomatic relations with Germany two days later, and, along with the Zimmermann Telegram, led the U.S. entry into the war two months later on the side of the Allied Powers.
Attempts to destroy evidence of German crimes
During World War II, after occupying France, Nazis seized Allied documentation regarding German war crimes in World War I and destroyed monuments commemorating them.
Executions of Kiev Jews by German army mobile killing units (Einsatzgruppen) near Ivangorod, Ukraine, 1942. The photo was mailed from the Eastern Front to Germany and intercepted at a Warsaw post office by Polish resistance member, Jerzy Tomaszewski who collected documentation on Nazi war crimes. The original German inscription on the back of the photograph reads, "Ukraine 1942, Jewish Action [operation], Ivangorod." 1942.
it should be noted that, as far as wartime actions against enemy nationals are concerned, the  Genocide Convention added virtually nothing to what was already covered (and had been since the Hague Convention of 1899) by the internationally accepted laws of land warfare, which require an occupying power to respect "family honors and rights, individual lives and private property, as well as religious convictions and liberty" of the enemy nationals. But the laws of war do not cover, in time of either war or peace, a government's actions against its own nationals (such as Nazi Germany's persecution of German Jews). And at the Nuremberg war crimes trials, the tribunals rebuffed several efforts by the prosecution to bring such "domestic" atrocities within the scope of international law as "crimes against humanity."
Wereth massacre. 17 December 1944, soldiers from 3./SS-PzAA1 LSSAH captured eleven African-American soldiers from 333rd Artillery Battalion in the hamlet of Wereth, Belgium. Subsequently the prisoners were shot and had their fingers cut off, legs broken, and at least one was shot while trying to bandage a comrade's wounds.
The campaign of extermination of Slavic population in the occupied territories. Several thousand villages were burned with their entire population (e.g., Khatyn massacre in Belarus). A quarter of the inhabitants of Belarus did not survive the German occupation.
Commando Order, the secret order issued by Hitler in October 1942 stating that Allied combatants encountered during commando operations were to be executed immediately without trial, even if they were properly uniformed, unarmed, or intending to surrender.
In addition, more than 90 villages and towns are recorded from the Hellenic network of martyr cities. During the triple German, Italian and Bulgarian, occupation about 800,000 people lost their lives in Greece (see World War II casualties).
Eichmann and his officers were responsible for the murder of most of the Jewish population in the ghettos of the territory of Czechoslovakia, and for the transport of men, women and children of all nationalities to extermination camps, for example KZ Auschwitz-Birkenau, May–June 1944.
^Colonial Genocide and Reparations Claims in the 21st Century: The Socio-Legal Context of Claims under International Law by the Herero against Germany for Genocide in Namibia, 1904-1908 (PSI Reports) by Jeremy Sarkin-Hughes
^Empire, Colony, Genocide: Conquest, Occupation and Subaltern Resistance in World History (War and Genocide) (War and Genocide) (War and Genocide) A. Dirk Moses -page 296(From Conquest to Genocide: Colonial Rule in German Southwest Africa and German East Africa. 296, (29). Dominik J. Schaller)
^The Imperialist Imagination: German Colonialism and Its Legacy (Social History, Popular Culture, and Politics in Germany) by Sara L. Friedrichsmeyer, Sara Lennox, and Susanne M. Zantop page 87 University of Michigan Press 1999
^Walter Nuhn: Sturm über Südwest. Der Hereroaufstand von 1904. Bernhard & Graefe-Verlag, Koblenz 1989. ISBN 3-7637-5852-6.
^Marie-Aude Baronian, Stephan Besser, Yolande Jansen, "Diaspora and memory: figures of displacement in contemporary literature, arts and politics", pg. 33 Rodopi, 2007,
^Samuel Totten, William S. Parsons, Israel W. Charny, "Century of genocide: critical essays and eyewitness accounts" pg. 51, Routledge, 2004,
^Dan Kroll, "Securing our water supply: protecting a vulnerable resource", PennWell Corp/University of Michigan Press, pg. 22