Reichswehreid

The Reichswehreid and from August 1934 Führereid was the name for three different versions of the oath of allegiance of the German Forces, called Reichswehr from 1919 to 1935, and then Wehrmacht until 1945.

1919–1933
The Original Reichswehreid came into effect on 14 August 1919, shortly after Reichspräsident Friedrich Ebert had signed the Weimar Constitution for the German Reich (the so-called Weimar Republic). The Treaty of Versailles limited the Reichswehr to a total of 100,000 men.

1933–1934
In January 1933, Adolf Hitler was appointed Reichskanzler and the Enabling Act and Gleichschaltung came in effect. As a result, a new wording was adopted on 1 December 1933:

It has to be noted that all references to the constitution and the office of Reichspräsident, then held by aging war hero Paul von Hindenburg, had already been removed. Instead, more emphasis was put on religion and patriotism.

1934–1945
In August 1934, after Hindenburg died, Hitler merged the offices of Reichsprasident and Reichskanzler, and declared himself Führer and Reichskanzler. War Minister Werner von Blomberg issued a new wording which became known as Führereid, the "Hitler oath":

Now Volk and Fatherland had been superseded by the person of Hitler himself, who would be Führer and supreme commander. In addition, the obedience was now to be unconditional.

The allegiance to Hitler, which millions of soldiers had to pledge, proved to be fateful as it choked opposition to him (July 20 Plot etc.).

In 1935, the Reichswehr was renamed Wehrmacht.

SS
The full Eidformel der Schutzstaffel (Oath of the SS) consisted of three questions and answers. The following text is cited from a primary source written by Heinrich Himmler.

The SS was initially founded to provide personal security for Hitler at party speeches, as well as the leaders he put in charge (Führerprinzip). The unshakable loyalty was made part of the SS' honour, as the motto "Meine Ehre heißt Treue" ("My honor is called loyalty"). Which was placed on the waffen ss belt buckle until they were disbanded after the war.

Bundeswehr
Currently, recruits of the Bundeswehr pledge the Gelöbnis after three months of basic training

Professional soldiers and officers of the Bundeswehr have to swear an oath with the same wording, but beginning with "Ich schwöre, ..." ("I vow ...").

The web site of the Bundeswehr points out that loyalty is pledged not to a person, but rather to the country, a novum in German military history.