The TLDR is the Dragoons were originally suppost to be a covert scouting force for the clans, however the leaders who were from Clan Wolf were given secret orders to prepare the IS for the clan invasion. Reason why is there was a political divide in the clans. One side was called the Crusaders, they believed that they were to have a full on crusade and take the Sphere to make a "New Star League " with the ideals of Nicholas Kerensky. The other side was the Wardens who believed that the Kerenskey's never ment for the clans to "retake the IS" but to stand apart from them as guardians above the common corruption, redy to intervene should the Sphere come under threat from internal or external forces.
The Wardens basically told the Leaders of the Dragoons to prep the US as best as possible so they did things like mixing in some clan tactics while fighting and going as far as reorganization of their mech forces from the IS traditional 4 mech "lance" to the Clan 5 mech "Star", so forces fighting them would get some experience against a clan like force. Then by the time of the clan invasion so many people had been gained and lost in the wolves they were basically going native.