The Klinkons are a genetic cast of Martian society. Indoctrination into the warrior cast triggers a metamorphosis resulting in the anatomical distinctions between Klinkons and normal Martian casts. The warrior cast was re-established by German nationalists that had been relocated from Earth to Mars in the early 1940s.
The re-emergence of this long forgotten caste has meant nothing but trouble for the British on Mars. The Klinkons have a strong loathing for anything British. The ostracized Germans that were their role models taught this hatred to the Martians. The Klinkons have retained the strict German discipline, the cultured German barbarity as well as the German sense of chivalry and Honor all of which are swords that cut both ways.