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Before the creation of the Lich King, the Horde and Alliance captured territory in Northrend. They created bases in Northrend and bombed each other's bases in the official Blizzard scenario map for Warcraft III called Bomber Command. Whichever force destroyed the other's base is unknown because the Lich King has since wiped out all the living from his icy domain.
Official Blizzard Warcraft III map: Warring Marines have taken over Icecrown Glacier. Command your bomber force to destroy your opponent's town while scrambling to defend your own.Battle.net link