The UED retcon makes no sense
The UED were introduced via retcon in BW, and were not originally planned as part of the franchise. The BW website at the time of release made no mention of the UED, but only stated that "Terran Emperor Mengsk I...must now turn his attention to...a conspiracy deep within his own ranks." In order to explain why the UED wasn't mentioned in the SC1 manual or OG campaigns, the BW manual states that the UPL secretly spied on Koprulu for centuries and then reformed as the UED when they saw the protoss and zerg ravage Koprulu. There are several problems with this retcon. How did the UPL secretly spy on Koprulu for centuries and without being discovered? In order for this to work, they would need human agents to infiltrate the colonies and remain both loyal and undetected over multiple generations. This is simply unbelievable, but it gets even more unbelievable from there. The UPL decided not only to secretly spy on Koprulu, but to keep Earth's and Koprulu's existence...