Cardassians.

The Cardassians were a humanoid species from the Alpha Quadrant. They were native to the planet Cardassia Prime, capital world of the Cardassian Union. Known throughout the Alpha Quadrant for their ruthlessness, the Cardassians became one of the greatest enemies of the United Federation of Planets and Klingon Empire when they joined the Dominion in 2373. the cardassians and dominions later went on to start the cardassian war.