Anything is possible, given time and the will.
The Colonial Union certainly had the will to destroy the Conclave’s fleet. The existence of the fleet was an intolerable threat; the Colonial Union decided to destroy it as soon as it learned of its existence. There was no hope that the Colonial Union could destroy the fleet in a toe-to-toe battle; with 412 battleship equivalents, it was larger than the entire CDF battle fleet. The Conclave fleet was assembled in whole only when removing the colonies, so there was the possibility of attacking each ship individually. But that would have been equally futile; each ship could be replaced in the fleet by its government, and it meant the Colonial Union would be picking a fight with each of the more than four hundred races in the Conclave, many of whom posed no real threat to the CU.
But the Colonial Union wanted to more than destroy the Conclave’s fleet. It wanted to humiliate and destabilize the Conclave; to strike at the heart of its mission and its credibility. The Conclave’s credibility came from its size and its ability to enforce its ban on colonization. The Colonial Union needed to hit at the Conclave in a way that would neutralize its size advantage and make a mockery of its ban. It had to strike at the Conclave at precisely the moment it was showing its strength: When it was attempting to remove a colony. One of our colonies.
Only the Colonial Union had no new colonies under threat from the Conclave. The most recent new colony, Everest, slipped in mere weeks before the Conclave’s ban. It was not under threat. Another colony would need to be founded.
Enter Manfred Trujillo and his crusade to colonize. The Department of Colonization had ignored him for years, and not simply because the Secretary of Colonization hated his guts. It had long been understood that the best way to keep a planet was to grow so many people on it that it was impossible to kill all of them efficiently. Colonial populations were needed to make more colonists, not more colonies. Those could be founded with surplus population from Earth. Barring the appearance of the Conclave, Trujillo could have campaigned to colonize until he was put into the ground and he wouldn’t have gotten anywhere.
But now Trujillo’s campaign became useful. The Colonial Union had kept the fact of the Conclave from the colonies themselves, as it had so many other things. Sooner or later, however, the colonies would need to be made aware of its existence; the Conclave was simply too big to ignore. The Colonial Union wanted to establish the Conclave as the enemy, in no uncertain terms. It also wanted the colonies to be invested in the struggle against the Conclave.
Because the Colonial Defense Forces were comprised of recruits from Earth—and because the Colonial Union encouraged the colonies to focus primarily on their local politics and issues rather than CU-wide concerns—colonists rarely thought of anything that didn’t involve their own planet. But by stocking Roanoke with colonists from the ten most-populated human planets, Roanoke would become the direct concern of more than half the population of the Colonial Union, as would its struggle against the Conclave. In all, a neat potential solution to a raft of issues.
Trujillo was informed that his initiative was being approved; then it was taken away from him. That was because Secretary Bell hated his guts. But it also served to remove him from the command loop. Trujillo was too smart not to have picked up the pieces if they were laid out in a way he could follow. It also helped create a political subtext that pitted the founding colonies against each other for a leadership position; this drew attention away from what the CU was really planning for the colony.
Add in two colony leaders dropped in at the last moment, and no one in Roanoke’s command structure would have the context to muck up the Colonial Union’s plan: to create the time and the opportunity to destroy the Conclave’s fleet. Time created by hiding Roanoke.