The Imperial Romulan State was a Romulan state founded by Donatra, formerly a commander in the Romulan Imperial Fleet, in late 2380 as a separate entity in opposition to the Romulan Star Empire under Praetor Tal'Aura. (ST novel: Articles of the Federation)
The Imperial Romulan State came about as a result of political schism in the Romulan Star Empire following Shinzon's coup in 2379. Several groups vied for power, including those led by two of the group of conspirators that helped bring Shinzon to power; Commander Donatra, and Senator Tal'Aura - the latter who was made the new Praetor. Donatra retained control and support over much of the Imperial Fleet, and put her political allegiance with Braeg, her lover, a former admiral, and Tal'Aura's political adversary. (TNG novel: Death in Winter)
Braeg orchestrated civil unrest in Victory Square on Romulus to try and force Tal'Aura out of office. But Braeg's rebellion was crushed when Tal'Aura brought in heavy weaponry to quell the crowd, prompting Braeg to surrender rather than allow a massacre. For Braeg's treason Tal'Aura had him poisoned and thus cemented Donatra's hatred and opposition to her. (TNG novel: Death in Winter; TTN novel: Taking Wing)
The power struggle between Donatra and Tal'Aura continued for about a year until finally in December of 2380, Donatra consolidated her powerbase and made a move against the Star Empire under Tal'Aura; on Achernar Prime she declared the existence of the Imperial Romulan State, with herself as its Empress. Using the parts of the military loyal to her, she took control of Achernar and several other planets, including Xanitla, Ralatak, and Virinat. These worlds were the primary agricultural planets of the Star Empire, which effectively meant that Donatra now effectively held the Empire's food supply hostage. (ST novel: Articles of the Federation)
The state was almost immediately recognized by the Klingon Empire, who were delighted at the prospect of the Romulans being fractured further. Although the United Federation of Planets initially refused to intervene in what it considered an internal Romulan affair, even as it offered humanitarian aide to hungry Romulans upon the loss of their farming planets, by early 2381 the Federation was forced to recognize the sovereignty of the Imperial Romulan State as a result of pressure from the Klingons and a need to show solidarity with its ally. (ST novel: Articles of the Federation; ST - Destiny novel: Mere Mortals)
The Federation and Imperial Romulan State established ambassadorships to one another's states, with Donatra appointing former warbird commander Jovis as her ambassador to the Federation. During the Borg invasion of that year, Jovis commented to Federation President Nanietta Bacco that Donatra wished to open a new era of peace with the Federation. The strength of that desire was demonstrated a short while later when the Imperial State warbird Verithrax sacrificed itself to save the Federation planet Ardana from Borg attack. (ST - Destiny novels: Mere Mortals, Lost Souls)
In the wake of the Borg invasion, the Federation's resources were stretched thin and the aid they had been providing to Romulus since Shinzon's coup was considered a resource they could use elsewhere. But despite the Star Empire's desperate need for food, Donatra refused to trade with Tal'Aura. The Federation sent a variety of diplomats and Starfleet captains for talks with Donatra, finally recruiting Professor Sonek Pran to meet with her in the hope of convincing her to start trade relations between the two Romulan states and providing the Federation some relief.
Where others had failed, Pran succeeded in convincing Donatra that she had already won her feud with Tal'Aura. Seeing that her ultimate goal was to reunite the Romulan people as Tal'Aura's power crumbled, Pran told her that the Empire did not have enough military force to engage the State in open war. With the State having a stranglehold on Romulan food resources, Pran argued that if Donatra were to trade with the Empire, the people would be all too aware of who was responsible for them being fed. However when Donatra tried to open talks with Tal'Aura, all she got was rejection.
A short while later, Tal'Aura's motivations for rebuffing Donatra were revealed: the Star Empire had become members of a new interstellar alliance known as the Typhon Pact: a group of nations united in currency, trade and technology in opposition to the Federation and the Klingons. In response, the Pact's competition invited several neighboring powers including the Imperial Romulan State to attend a summit to discuss an expansion of the Khitomer Accords and create a new group to counter the Pact. Donatra immediately accepted this offer. (ST novel: A Singular Destiny)
As of late 2381, however, no official relationship had been formally created between the Federation and the Imperial Romulan State aside from discussions of expanding their relationship. This had been seen by Empress Donatra as a problem especially when she came under an attack by Praetor Tal'Aura. Tal'Aura launched a propaganda campaign against the Imperial Romulan State and Donatra herself calling for reunification of the Romulan Empires. When Donatra agreed to meet with Tal'Aura, she was quickly arrested on fabricated evidence implicating her in the attempted murder of Ambassador Spock of Vulcan. Without a leader, the Imperial Romulan State was reabsorbed into the Romulan Star Empire one month following Donatra's arrest. (ST - Typhon Pact novel: Rough Beasts of Empire)
In 2381 Donatra formed the Imperial Romulan State when she and sections of the military loyal to her took control of several Romulan agricultural worlds. She declared herself Empress of the Imperial Romulan State with her capital planet as Achernar Prime.
In 2383, the Star Empire's forces under command of Fleet Commander Tomalak attacked Donatra's fleet at Xanitla. Donatra's forces were victorious in the battle, and as an additional blow to the Star Empire Admiral Taris and the twelve ships under her command defected to the Imperial State. By the following year this crushing defeat pushed Tal'Aura to reluctantly open peace talks with the Imperial State to establish borders and a neutral zone. Donatra sent Taris to Romulus as her representative but Tal'aura was assassinated shortly after. Donatra strongly refuted any claims of her involvement in the assassination and recalled Taris in preparation for any subsequent offensive.
In 2385, in the aftermath of Tal'Aura's assassination Donatra used the opportunity to win the hearts of the Romulan people by delivering food aid to non-military worlds in the Star Empire. Together with Proconsul Sela and Tal Shiar leader Rehaek, Donatra agreed to fold the worlds of the Imperial Romulan State back into the Star Empire, while she retained command of the military - keeping most of her forces away from Romulus in case the peace did not hold. The newly reunited Romulan Senate then appointed Senator Chulan the new Praetor. (ST website: The Path to 2409)
- The Star Trek Online timeline, The Path to 2409 does not incorporate the events of the Star Trek: Destiny trilogy or A Singular Destiny and subsequently makes no mention of the political situation brought about by the formation of the Typhon Pact. Instead, the State is founded in 2381 rather than 2380, and the Romulan situation remains a largely internal matter.