The Imperial Invasion of Mon Calamari was one of the first invasion and enslavement campaigns instigated by the Galactic Empire. It resulted in the conquest of Mon Calamari and the enslavement of the Mon Calamari and Quarren species. Moff Willhuff Tarkin, who was soon to be promoted to Grand Moff, led the invasion.
Following the dissolution of the Galactic Republic, the newly formed Galactic Empire began to spread it's power across the Universe. As the Imperial war machine continued to mature and expand, new resources were needed. Slavery, to the Imperials, would be a key component in this buildup. Like the Wookiees of Kashyyyk, the Vulcans of Vulcan, and the Klingons of Qu'onos, the Mon Calamari and Quarren were considered ideal slaves. The world's massive, effective, well-known shipyards and it's location near the Star Trek dimension served as the perfect site of a Imperial base.
The Mon Calamari and Quarren both attempted a peaceful settlement with the Empire, but that was rejected. The world would bear the full force of a Imperial invasion, commanded by Moff Willhuff Tarkin, one of the Empire's most powerful officials and supervisor of the Death Star construction project.
With a planetary shield generator covering their world, the Mon Calamari and Quarren foolishly believed they could resist any Imperial attacks. However, Bothan spies, disguised as Quarren, sabotaged the shield generators, thus leaving the planet vulnerable. A fleet of Imperial Star Destroyers, commanded by Tarkin, appeared over the world. Immediately, the Mon Calamari and Quarren ground defenses, consisting of little more then machine gun turrets, were promptly destroyed, the Mon Calamari Shipyards fell into Imperial possession, and stormtroopers landed on the world, quickly enslaving the Mon Calamari and Quarren. The Mon Calamari High Council and the Quarren Clans were forced to surrender, thus bringing the world under formal Imperial control.
Imperial occupation forces immediately moved onto the world. The Mon Calamari and Quarren slaves were forced to work at their own home-world's shipyards, on the Death Star construction project, and on other Imperial projects. The Empire would use brutal force to maintain order on the world. When a group of Mon Calamari slaves revolted in 2 BBY, the Empire responded by destroying a floating city on the world, killing hundreds of thousands. This squashed the rebellion.