Taking advantage of its large fleet of heavy ships Cartel launched a massive attack against the Federation. What they didn’t know is that a third party was already prepared to strike as well - aliens. Cartel’s flagship was heavily damaged during the attack bringing invasion to a halt.
Cartel can’t resume its campaign without the leading ship - and that opportunity was fully realised by the Federation. The dreadnought must not be restored - this is the only way to avoid a full scale war on two fronts!