Wehrmacht
Origin: 

Etymology: The German term "Wehrmacht" stems from the compound word of German: wehren, "to defend" and Macht, "power, force". It has been used to describe any nation's armed forces; for example, Britische Wehrmacht meaning "British Armed Forces". The Frankfurt Constitution of 1849 designated all German military forces as the "German Wehrmacht", consisting of the Seemacht (sea force) and the Landmacht (land force). In 1919, the term Wehrmacht also appears in Article 47 of the Weimar Constitution, establishing that: "The Reich's President holds supreme command of all armed forces [i.e. the Wehrmacht] of the Reich". From 1919, Germany's national defense force was known as the Reichswehr, a name that was dropped in favor of Wehrmacht on 21 May 1935.
While the term Wehrmacht has been associated, both in the German and English languages, with the German armed forces of 1935–45 since the Second World War, before 1945 the term was used in the German language in a more general sense for a national defense force. For instance, the German-aligned formations of Poles raised during the First World War were known as the Polnische Wehrmacht ('Polish Wehrmacht', 'Polish Defense Force') in German.

Background: In January 1919, after World War I ended with the signing of the armistice of 11 November 1918, the armed forces were dubbed Friedensheer (peace army). In March 1919, the national assembly passed a law founding a 420,000-strong preliminary army, the Vorläufige Reichswehr. The terms of the Treaty of Versailles were announced in May, and in June, Germany signed the treaty that, among other terms, imposed severe constraints on the size of Germany's armed forces. The army was limited to one hundred thousand men with an additional fifteen thousand in the navy. The fleet was to consist of at most six battleships, six cruisers, and twelve destroyers. Submarines, tanks and heavy artillery were forbidden and the air-force was dissolved. A new post-war military, the Reichswehr, was established on 23 March 1921. General conscription was abolished under another mandate of the Versailles treaty.
The Reichswehr was limited to 115,000 men, and thus the armed forces, under the leadership of Hans von Seeckt, retained only the most capable officers. The American historians Alan Millet and Williamson Murray wrote "In reducing the officers corps, Seeckt chose the new leadership from the best men of the general staff with ruthless disregard for other constituencies, such as war heroes and the nobility." Seeckt's determination that the Reichswehr be an elite cadre force that would serve as the nucleus of an expanded military when the chance for restoring conscription came essentially led to the creation of a new army, based upon, but very different from, the army that existed in World War I. In the 1920s, Seeckt and his officers developed new doctrines that emphasized speed, aggression, combined arms and initiative on the part of lower officers to take advantage of momentary opportunities. Though Seeckt retired in 1926, his influence on the army was still apparent when it went to war in 1939.
Germany was forbidden to have an air force by the Versailles treaty; nonetheless, Seeckt created a clandestine cadre of air force officers in the early 1920s. These officers saw the role of an air force as winning air superiority, strategic bombing, and close air support. That the Luftwaffe did not develop a strategic bombing force in the 1930s was not due to a lack of interest, but because of economic limitations. The leadership of the Navy led by Grand Admiral Erich Raeder, a close protégé of Alfred von Tirpitz, was dedicated to the idea of reviving Tirpitz's High Seas Fleet. Officers who believed in submarine warfare led by Admiral Karl Dönitz were in a minority before 1939.
By 1922, Germany had begun covertly circumventing the conditions of the Versailles treaty. A secret collaboration with the Soviet Union began after the Treaty of Rapallo. Major-General Otto Hasse traveled to Moscow in 1923 to further negotiate the terms. Germany helped the Soviet Union with industrialization and Soviet officers were to be trained in Germany. German tank and air-force specialists could exercise in the Soviet Union and German chemical weapons research and manufacture would be carried out there along with other projects. In 1924 a fighter-pilot school was established at Lipetsk, where several hundred German air force personnel received instruction in operational maintenance, navigation, and aerial combat training over the next decade until the Germans finally left in September 1933. However, the arms buildup was done in secrecy, until Hitler came to power and it received broad political support.

Nazi rise to power: After the death of President Paul von Hindenburg on 2 August 1934, Adolf Hitler assumed the office of President of Germany, and thus became commander in chief. In February 1934, the Defence Minister Werner von Blomberg, acting on his own initiative, had all of the Jews serving in the Reichswehr given an automatic and immediate dishonorable discharge. Again, on his own initiative Blomberg had the armed forces adopt Nazi symbols into their uniforms in May 1934. In August of the same year, on Blomberg's initiative and that of the Ministeramt chief General Walther von Reichenau, the entire military took the Hitler oath, an oath of personal loyalty to Hitler. Hitler was most surprised at the offer; the popular view that Hitler imposed the oath on the military is false. The oath read: "I swear by God this sacred oath that to the Leader of the German empire and people, Adolf Hitler, supreme commander of the armed forces, I shall render unconditional obedience and that as a brave soldier I shall at all times be prepared to give my life for this oath".
By 1935, Germany was openly flouting the military restrictions set forth in the Versailles Treaty: German rearmament was announced on 16 March with the "Edict for the Buildup of the Wehrmacht" (German: Gesetz für den Aufbau der Wehrmacht) and the reintroduction of conscription. While the size of the standing army was to remain at about the 100,000-man mark decreed by the treaty, a new group of conscripts equal to this size would receive training each year. The conscription law introduced the name "Wehrmacht"; the Reichswehr was officially renamed the Wehrmacht on 21 May 1935. Hitler's proclamation of the Wehrmacht's existence included a total of no less than 36 divisions in its original projection, contravening the Treaty of Versailles in grandiose fashion. In December 1935, General Ludwig Beck added 48 tank battalions to the planned rearmament program. Hitler originally set a time frame of 10 years for remilitarization, but soon shortened it to four years. With the remilitarization of the Rhineland and the Anschluss, the German Reich's territory increased significantly, providing a larger population pool for conscription.

Personnel and recruitment: Recruitment for the Wehrmacht was accomplished through voluntary enlistment and conscription, with 1.3 million being drafted and 2.4 million volunteering in the period 1935–1939. The total number of soldiers who served in the Wehrmacht during its existence from 1935 to 1945 is believed to have approached 18.2 million. The German military leadership originally aimed at a homogeneous military, possessing traditional Prussian military values. However, with Hitler's constant wishes to increase the Wehrmacht's size, the Army was forced to accept citizens of lower class and education, decreasing internal cohesion and appointing officers who lacked real-war experience from previous conflicts, especially World War I and the Spanish Civil War.
The effectiveness of officer training and recruitment by the Wehrmacht has been identified as a major factor in its early victories as well as its ability to keep the war going as long as it did even as the war turned against Germany.
As the Second World War intensified, Kriegsmarine and Luftwaffe personnel were increasingly transferred to the army, and "voluntary" enlistments in the SS were stepped up as well. Following the Battle of Stalingrad in 1943, fitness and physical health standards for Wehrmacht recruits were drastically lowered, with the regime going so far as to create "special diet" battalions for men with severe stomach ailments. Rear-echelon personnel were more often sent to front-line duty wherever possible, especially during the final two years of the war where, inspired by constant propaganda, the oldest and youngest were being recruited and driven by instilled fear and fanaticism to serve on the fronts and, often, to fight to the death, whether judged to be cannon fodder or elite troops.

Prior to World War II, the Wehrmacht strove to remain a purely ethnic German force; as such, minorities within and outside of Germany, such as the Czechs in annexed Czechoslovakia, were exempted from military service after Hitler's takeover in 1938. Foreign volunteers were generally not accepted in the German armed forces prior to 1941.