A is for Algeron, Treaty of. Signed in good faith by the Federation. Only somewhat so by the Romulans.
B is for Battle of Cheron, which was either the climactic skirmish of the Earth-Romulan War in 2160 or the last conflict between the Romulans and the Federation that happened in 2311 and preceded the Empire's withdrawal into isolation for the next half-century.
C is for Commander. The rank held by the first Romulan we ever saw.
D is for D'Deridex-class Warbird...twice as long as a Galaxy-class Federation starship.