Ekos was the homeworld of the Ekosian race of humanoids, and the inner of two M-class planets orbiting an unnamed star, sister to the outer planet Zeon.
In the mid-23rd century, Ekos was in the throes of anarchy. Dispatched by the United Federation of Planets to the upheaval in the mid-2260s as a cultural observer, noted historian John Gill chose to abandon the non-interference policy, believing a modified form of National Socialism could be installed to impose order without the disastrous results wrought to German culture in the years leading up to Earth's Second World War. Gill then proceeded to establish a passive version of the Nazi state, complete with recreations of such notorious German organizations as the SS, using the forms, symbols and uniforms of 20th century Earth.
Soon enough, however, the inherent opportunities for abuse of power within such a system reverted the Ekosian government to the established fascist pattern and the Ekosians began a genocide campaign against the neighboring planet Zeon. (TOS: "Patterns of Force")