Well, I think I just figured out why the aliens suddenly just stopped their attacks as they did...
Even from the first transit into the Gliese 109 system, something was obviously amiss. Dozens of wrecks were littered around the binary system, and only about half of those wrecks matched records of known Haora ships. No active sensor contacts were detected, so survey operations were warily commenced. On approach to the innermost planet of the companion star, passive sensors detected a small-medium population, perhaps 10mil worth of colonists. Naval Intelligence hypothesised that this system was probably a major outpost of some sort for the Haora Empire which had seen some major action recently. Carrier Group 1 was dispatched to investigate and ultimately annex the colony.
After CG1 arrived in orbit of the planet, a laser bombardment was ordered which continued for all of 15 seconds after which the colony surrendered. The party that was sent down to the surface however was greeted with a nightmarish visage - after passing below the obscuring cloud layer, a thoroughly irradiated landscape could be seen. Countless craters pockmarked the land, and the ground was liberally covered with rubble from what was presumably once a planet-wide cityscape. Nuclear winter had well and truly set in, with average temperatures well below 100C measured at the surface. This planet had seen some serious nuclear bombardment.
The "colony" that had surrendered was actually a small portion of the planetary city that had somehow survived more or less intact. The ~9million civilians that were still alive on the planet divulged the location of some impressive fuel, maintenance and mineral stashes that had survived bombardment by virtue of being stored deep underground, however it was also learned that none of the planet's industry had been left untouched. It seems that whatever force had attacked previously was careful to ensure the Haora would never be able to rise above the Stone Age again. In any case, the sheer level of radiation that still lingered completely rendered any manufacturing equipment useless, and any survivors would be sterilised anyway, so the Haora race was doomed to a slow death.
Naval Intelligence is now prioritising salvage operations in the Gliese 109 system in an attempt to gain any information as to the identity and capabilities of this new alien power.