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.
The Herero and Namaqua Genocide is considered to have been the first genocide of the 20th century. It took place between 1904 and 1907 in German South-West Africa (modern day Namibia), during the scramble for Africa.
On January 12, 1904, the Herero people, led by Samuel Maharero, rebelled against German colonialism. In August, General Lothar von Trotha of the Imperial German Army defeated the Herero in the Battle of Waterberg and drove them into the desert of Omaheke, where most of them died of thirst. In October, the Nama people also rebelled against the Germans only to suffer a similar fate.
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.
Poison gas was introduced by Imperial Germany, and was subsequently used by all major belligerents in the war against enemy soldiers, in violation of the 1899 Hague Declaration Concerning Asphyxiating Gases and the 1907 Hague Convention on Land Warfare, which explicitly forbade the use of "poison or poisoned weapons" in warfare.
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.
During World War II, after occupying France, Nazis seized Allied documentation regarding German war crimes in World War I and destroyed monuments commemorating them.
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."—Telford Taylor
(see also List of massacres in Greece)
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).
Asperg. Sinti and Roma children about to be deported, 22 May 1940.
Iaşi. Jewish bodies, 29 June 1941.
Reichskommissariat Moskau. Jewish women and children been forced out of their homes. A soldier in Romanian uniform is marching along as a guard, 17 July 1941.
Members of the 21st Latvian Police Battalion assemble a group of Jewish women for execution on a beach near Liepāja, 1941.
Warsaw ghetto, 1940/1943.
Warsaw Ghetto Uprising – Photo from Jürgen Stroop Report to Heinrich Himmler from May 1943. The original German caption reads: "Askaris used during the operation". Two Askari or Trawniki guards, peer into a doorway past the bodies of Jewish children killed during the suppression of the Warsaw ghetto uprising.
Memorial to the murdered children of Lidice.
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