In an alternate timeline theorized by Khitomer Alliance temporal scientists, the Vulcan Star Empire was an interstellar nation-state controlled by the Vulcans. In this reality, the Vulcans never embraced Surakian philosophy and instead formed a star empire, analog to the Romulan Star Empire of the primary universe. (STO - Iconian War mission: "Butterfly Effect")
History and specifics
When the Iconian War raged in 2410, the desperate Khitomer Alliance built a Annorax-class temporal weapon ship to change the timeline in the Alliance's favor. Before the ship, the KIS Annorax, was launched, Alliance personnel ran simulations at the Krenim research facility in the Kyana star system. These simulations included holodeck scenarios of the potential timelines.
In one version related to this timeline, the Dewans of Dewa III developed warp engines and rose to power. They conquered most of the Beta Quadrant but were forced back by Vulcan civilization that never embraced Surakian logic. The Vulcan Star Empire enslaved what in the primary timeline was Federation and Klingon Empire space.
When the Vulcans encountered the Klingons in the 22nd century, they found them a primitive farmer culture with some advances in epic poetry. By the present day of the simulation, the Vulcan Star Empire was embroiled in a to-the-death-struggle with the Dominion.