Born in Lublinitz (now Lubliniec, Poland) in Upper Silesia, the son of a veterinarian, Lammers completed law school at the universities of Breslau (today, Wrocław) and Heidelberg, obtained his doctorate in 1904, and was appointed judge at the Amtsgericht (district court) of Beuthen (Bytom) in 1912.

[2] Lammers joined the Nazi Party with an effective date of 1 March 1932 (membership number 1,010,355) and achieved rapid advancement.

[3] At the recommendation of Interior Reichsminister Wilhelm Frick, he became the centre of communications and chief legal adviser for all government departments.

The historian Martin Kitchen explains that the centralization of power accorded to the Reich Chancellery and therefore to its head made Lammers become "one of the most important men in Nazi Germany".

Hitler agreed to the creation of a three-man committee with representatives of the state, the army and the party in an attempt to centralise control of the war economy and over the home front.

Seeing it as a threat to their power, Joseph Goebbels, Albert Speer, Hermann Göring and Heinrich Himmler worked together to bring it down.

[9] In April 1945, Lammers was arrested by SS troops during the final days of the Nazi regime, in connection with the upheaval surrounding Hermann Göring.

On 23 April, as the Soviets tightened the encirclement of Berlin, Göring consulted Luftwaffe General Karl Koller and Lammers.

[12][13] Lammers was taken prisoner by American forces,[14] but in the meantime, his wife, Elfriede (née Tepel), committed suicide near Obersalzberg (the site of Hitler's mountain retreat) in early May 1945, as did his daughter, Ilse, two days later.

[16] Lammers reported to the Allies that Nazi kingpins and high-ranking Wehrmacht officers received lavish gifts, severance packages, expropriated estates and huge cash awards.