The Vertian crisis was an interstellar conflict that took place in March-April 2163, between the Vertians and a number of different nations including the United Federation of Planets, with the interference of criminal organizations.
The Vertians didn't have any hostile or expansionist goals, they simple perceived other species to be non-sentient because they didn't share the Vertian way of communication, so they started capturing different ships and their crews to study them and develop defenses against them. However these species took this as aggression, and the Orion crime lord Navaar and her allies saw this as an opportunity to force the newly formed Federation into a war so they could continue their illicit operations in the region.
The Vertians has been conducting their "scientific missions" for decades before the conflict. For example the Enterprise in 2151 and the IGS Docana in 2160 fell victim to these attacks, although without casulties. Others were less fortunate, over the years several starships, belonging to different species vanished in and around the Kandari sector, but they were regarded as separate incidents, pirate of Romulan attacks.
After the formation of the Federation and the defeat of the Romulan Star Empire in 2161 however, trade and other kind of space trafic increased in the region, as well the number of the attacks. The link was made, after the USS Endeavour under the command of Captain T'Pol rescued an Axanar starship from a Vertian attack in January of 2163. T'Pol, who was the first officer of the Enterprise during it's encounter with the Vertians, immediately recognised their methods. She informed Starfleet Command of the incident and the Axanar informed their government, and the information started to spread. In the following months several species including Rigelians, Ithenites, Xarantine and Malurians, came forward with information about similar attacks, and in March of that year they asked the Federation for help.
The Federation hosted a negotiation on Deneva colony in March. Among the participants were Federation Defense Commissioner Min glasch Noar, Andorian Starfleet Chief of Staff Admiral Thy'lek Shran and the famed Admiral Jonathan Archer. The non-aligned world were represented among others by Ambassador Boda Jahlet of Rigel, the Xarantine Orav Penap and Malurian Dular Garos. The later two were secretly working for the Three Sisters, Navaar, D'Nesh and Maras, in the hopes manipulating the Federation officals into starting a war. To that end, Penap offered his hospitalities, which included Orion slave girls among others.
As the conclusion of the talks, Starfleet dispatched a task force to the Kandari sector so that in unison with the non-aligned worlds own forces could secure the region. The Rigelians offered that they could use Rigel V Orbital Spacedock as center of operations. The Starfleet task force mainly consisted of Andorian warships under the overal command of Admiral Shran, and on the field Commodore Nisverin th'Menchal lead the ships from his flagship the USS Vinakthen. However, Shran and Archer was content to resolve the situation without getting involved in another war.
The task force started the patrol the region. Several minor engagements took place, but the first major occurrence was the destruction of the USS Thejal. The ship was under the command of Captain Trenkanshent sh'Lavan, and engaged a Vertian ship on March 26th. After the Vertians retreated, the Malurian warship Rivgor under the command of Dular Garos offered their help in ambushing and capturing the attacker near an ice giant planet. Two days later the Vertians returned to capture the Thejal. The Rivgor entered the fight according to plan, but instead of disabling the Vertian ship they destroyed it, then turned their guns on the Thejal. The Malurians configured their weapons to Vertian frequencies to provoke the Federation forces into a more aggressive position.
Following the Thejal's destrution Commissioner Noar, who fell under the influence of Devna, started to organize a vote to relive Admiral Shran of command of the task force so they could retaliate against the Vertians in full force.
On April 2, the Endeavour and several task force ships disabled a Vertian ship. Shortly thereafter the USS Vinakthen and the Rivgro arrived on the scene and Commodore th'Menchal ordered the Vertian ship to be seized . A joint strike team from Vinakthen, Rivgro and Endeavour boarded the ship, but couldn't secure the entire vessel, so they took a number of prisoners and withdrew.
A few days later a sizable Vertian force intercepted and disabled the allied ships, demanding "the surrender of all crew." They of course ment, their own people, but Garos tried to convince Starfleet forces that the Vertians wanted all of them. He failed, and Shran ordered the Vertians to be released. As a final effort of sabotage, Garos held back his prisoners.
Lieutenant commander Hoshi Sato volunteered to accompany the Vertians back to their ships, because she and Captain T'Pol spent the prior days trying to communicate with their prisoners. T'Pol even melded with them, and showed them that they are sentient.
During this time on Rigel V, Admiral Archer and Charles Tucker III of Section 31 uncovered Penap's intentions and interrogated him. He confirmed their suspicions that his girls were controlling the Federation officials. With that evidence he was able to convince Commissioner Noar to stand down, just as he was about to force Shran into opening fire on the Vertians.
At this point Garos opened fire on the Vertians with Rivgor and they opened up on the entire task force. After the initial volley, Shran ordered all allied ships to only fire on Rivgor. The massive Malurian warship couldn't hold out very long, so Garos beamed his prisoners into space then ordered retreat hoping that he was successful in starting a war. Endeavour quickly maneuvered to pick them up, then Captain T'Pol decided to join Sato in her efforts to enlighten the Vertians about their sentience.
In the following week the two women succeeded in their task. The Vertians were highly ashamed that they harmed sentient beings, so they released all of their prisoners and agreed to stop their attacks if their past actions go without retaliation. After that, negotiations started to work out a permanent peace.
With that, the Orion Syndicate's first plot to hinder the Federation failed, and acting on the information that Tucker gained from Devna, Starfleet forces were able to stop the Orions from raiding a medical convoy. Also, with the end of Vertian attacks, space travel became much safer in that region, and opened up new sectors for exploration and expansion. This opportunity also paved the way for Starfleet's eventual encounter with the Ware. (ENT - Rise of the Federation novel: A Choice of Futures)