The Tomed Incident was a horrific act of terrorism recorded by history early in the year of 2311. History records that this incident cost many thousands of Federation lives when Romulan Admiral Aventeer Vokar, an extremist in the Romulan Imperial Fleet, ordered his ship, the Tomed, abandoned by all but six of the crew. From there, Vokar and his cohorts set course for the Foxtrot Sector in Federation space. Upon reaching their destination, the ship impacted with an asteroid base, and its quantum singularity drive caused a massive explosion due to the fact that singularity containment was lost while the warp field was still active, disrupting space-time throughout the sector and wiping out dozens of asteroid bases and at least one starship, the USS Agamemnon. Thousands of lives were lost, with only the USS Enterprise-B escaping destruction. Vokar apparently commited this heinous act in the hopes of prompting a war between the Federation and the Romulan Star Empire due to his long-standing Romulan chauvinism and imperialistic stances. The Tomed Incident nearly accomplished Vokar's goal before the Klingon Empire, previously neutral, sided with Federation forces, thus prompting the Imperial Fleet to retreat from the border.
Two months after the Tomed Incident, the Romulan Star Empire forced the Federation to sign The Treaty of Algeron that banned the development of cloaking technology within the Federation in return for the Star Empire's agreement to withdraw behind its borders and to recall all of its diplomatic missions and citizens, effectively isolating them on the astropolitical scene.
In reality, Vokar did not cause the Tomed Incident, and only the lives of the six Romulans were lost. Capt. John Harriman and Starfleet Intelligence operatives Elias Vaughn and Drysi Gravenor of the Federation stowed aboard the Tomed and tricked most of the crew into abandoning ship. From there, they hijacked the Tomed, ramming it into the Foxtrot Sector asteroid base -- a base that had, like the Agamemnon and the other asteroid bases, been previously emptied of all crew but equipped with special devices designed to emit artificial lifesigns. The deaths of thousands of Starfleet officers from across the Federation had, in the previous year, been covered up, and those officers were then recorded as having all transferred to the Foxtrot bases and to the Agamemnon, completing the fabrication. The Starfleet operatives escaped to the Enterprise, but Vokar and his crew were killed. (TLE novel: Serpents Among the Ruins)
- As of stardate 41986.0 (approximately December 2364), Starfleet and the Federation had not had contact with the Romulans for 53 years, 7 months, and 8 days (TNG episode: "The Neutral Zone"). This means they last communicated with the Romulan government in the middle of the year 2311. This contact would presumably be the ratification of the Treaty of Algeron, which would follow the Tomed Incident by only a few months, at the most.