Elas was the inner planet of the Tellun Star System, homeworld of the Elasian people, located some 0.037 light-years from the outer planet Troyius.
Elas and its neighboring planet, Troyius, had been at war for many centuries. Peace was finally established in 2268, as Elaan, Dohlman of Elas, married the ruler of Troyius as the final gesture of peace between the two planets. (TOS:"Elaan of Troyius")
Elas is not a warp capable civilization. It would seem that the prime directive should had forbidden interference by the Federation. We can only assume that the planet was already culturally contaminated, possibly by contact with a Troyian vessel.