The GNE was founded after a military Coup in 3039 BCE. It spread Yyierianism and "equality" to citizens. they held 2500 worlds at it's height.
The GNE was somewhat oppressive, but the government wasn't necessarily the issue, but the ideology. Another issue was the fact that Technology had been stagnating for centuries due to the extremely low pay of it's scientist community which all but dissappeared. this eventually led to it's defeat after the siege of Castieliaris, where Unionist raiders known as the Kandaris Horde, sieged and took over Castielaris with new Psi-Beam technology sold to them by the Boreluzians, though the Empire fell they still held around 1700 of it's worlds, before a regime change took place.