In 2387, Starfleet established Starbase 900 at the planet Tast in the Delta Quadrant, on a mission to explore and gain a presence in that quadrant. A year later, the United Federation of Planets agreed in the Treaty of Romulus to share the starbase with the Klingon Empire and the Romulan Star Empire.

The Federation is leading the mission, but it is now a joint alliance of the three great powers of the Alpha Quadrant. Starbase 900 is to be shared by the Federation, including provision for embassies for the Romulan Star Empire and the Klingon Empire, as well as quarters for supporting staff, including from the Imperial Defense Forces of the Klingons, and the Star Navy of the Romulans. The Klingons will also share in providing security for the station and the mission.

In 2428, the alliance expanded when the Cardassian Union joined the Treaty of Romulus on a provisional basis. The Cardassian government under the now-sovereign Detapa Council will establish an embassy and send support staff.

These four factions are allied in the Delta Quadrant, and at peace in the Alpha and Beta Quadrants, but they all remain independent, functioning states back home.