Did you know...
...that the Earth-Romulan War that took place between 2155–2160 was a result of an escalating series of covert and hostile operations undertaken by the Romulan Star Empire against members who would later become the United Federation of Planets. These conflicts came to a head on October 14, 2156, when Romulan forces attacked and destroyed the USS Patton
, an event that signaled the beginning of the war. After staggering losses, Earth Alliance and the Romulan Star Empire negotiated a ceasefire and treaty, which was later re-enforced after the founding of the United Federation of Planets by the signing of the Federation/Rihannha Non-Aggression Pact. To this day, the treaty remains unbroken and there is limited to no contact between Earth and the Romulan Star Empire.
As the United Federation of Planets was founded on August 12th, 2161, it is argued that the actions necessitated by the founding members to combat the Empire led directly to the alliances that allowed the Federation to form (source