Dublin was the capital city of Ireland in the Universal Century timeline.
Immediately after the Gryps Conflict, the Earth Federation leadership was transferred to Dublin. During part of the final stages of the First Neo Zeon War, to force the Earth Federation to follow to her demands, Haman Karn maneuvered a colony into Earth Orbit. Her target was Dublin, the city that has been the capital of Ireland since the 12th century AD and now home to the Federation leadership. Despite the attempts of the AEUG and Karaba, there was no way to halt it.
The leaders of the Federation in Dublin abandoned the city, sending no forces to help evacuate since they saw it as a means of population control. They were able to flee on private planes leaving thousands if not millions to die (the population of Dublin as of the historical 2009 AD census was just over a million and is likely much higher in the Universal Century). Despite attempts for the civilians to flee on their own through alternative transportation (ships, planes etc.), Neo-Zeon forces were sent to prevent the civilians from evacuating Dublin to help strengthen the resolve of this operation's purpose, destroying several vehicles in the process and killing the civilians aboard them.
In response, the Argama and Karaba were sent to evacuate, with the Gundam Team covering. During the battle with the Neo Zeon forces under Glemy Toto, Karaba leader Hayato Kobayashi was killed in the fire fight with Neo Zeon Ace Rakan Dahkaran.
Ultimately, the evacuation was partially successful. There was no way of evacuating all the people in Dublin, but several thousand were able to survive after being put onto Karaba's flagship the Audhumla. When the colony dropped, it flattened everything in Dublin and created earthquakes and eruptions in the area. However, the area was spared the fate of Sydney, Australia, which had been destroyed in the One Year War, since the colony didn't explode, but fell apart, allowing the the damage to be less severe. Additionally, the explosion killed the Karaba pilots on board the Audhumla, but the members of the Gundam team (minus Judau Ashta) boarded the plane and safely took control, saving the civilians on board.