The Federation-Alliance war was a dual-Quadrant-wide war in the 28th century. The aggressors in this war were a group of Alpha and Beta Quadrant powers banded together against the Federation, calling themselves The Alliance.
For years, small skirmishes and planetary conquests against Federation member worlds and surrounding space would take place, pushing the Federation's border's back and shrinking its territories. A lack of hope and power led them to secede to the Alliance until the year 2752, when Admiral Thomas Garrison took a chance and decided to co-ordinate a counter attack. By this action, war had been officially declared. (Star Trek: 001: "New Beginnings", "Red Sand, Dark Tide")