The Third Battle of Acktundo was a full-scale assault by the Der Hintergedanke and their new allies, the Nagai Alliance, to reacquire the Outer Rim world of Acktundo. It saw the defeat of the Republic/Jedi/Senex-Juvex led forces.
After the battle, the Nagai Alliance was officially incorporated into the Der Hintergedanke.
After the Republic's fleet had been destroyed, the Der Hintergedanke sent its land troops onto the planet to weed out any and all resistance. Unfortunately, that resistance was deeply entrenched within the caverns of the Kahl Wastelands and refused to come out, no matter how much firepower or manpower was sent to evict them. Even the famed Mandalorian shocktroopers fell to the determination of the cornered soldiers and Jedi.
Darth Verraeter, growing weary of the endless hit and runs, asked several of his most trusted advisors for plans on what to do next. Finster der Alchimist, Verraeter's advisor on all things related to the ancient Sith, advised him to conceal his fleet and wait for the Republic to try to flee the planet and then come out of the concealment to destroy them utterly. Verraeter liked the idea and pulled his men back, while he and several other Sith Lords focused on hiding them.
After several days, the Jedi and Republic finally felt they could leave without fear of reprisal and attempted to flee, but were met by the hidden cult fleet, and vaporized.