After the One Year War ended, Side 3 was allowed to nominally maintain independence from Earth but a new government was set up by the Earth Federation to be more favorable towards it, the Republic of Zeon.
Following the end of the Second Neo Zeon War, the Earth Federation began to make plans to annex Side 3 back into themselves. In response, a faction of hardliners in the Republic of Zeon government, led by Defense Minister Monaghan Bakharov, began to conspire to undermine the Federation so the Republic of Zeon could keep its independence. To this end, they funded a project to create a Cyber-Newtype clone of Char Aznable to lead a third Neo Zeon resurgence which produced Full Frontal. Full Frontal's Neo Zeon waged a war to topple the Earth Federation in order to trigger mankind's migration into space.
Though Full Frontal and Neo Zeon were eventually crushed, a contingent of Republic of Zeon forces posing as Neo Zeon remnants continued to wage a guerrilla war against the Earth Federation. These forces were led by Zoltan Akkanen, a failed clone of Char from the same project that produced Full Frontal, and received instruction directly from Monaghan Bakharov. These forces were eventually defeated by the Earth Federation Forces, but Monaghan was able erase any connection between the Republic and Zoltan's forces.
Principality of Zeon