Star Crusader: Siege of Kalar. Star Crusader, #6

Nate and his friends in Ironclad Squadron are returning to the fleet when they detect a mysterious signal. Sensing a trap, Colonel Gun sends Nate out alone in his captured fighter to scout the source. The signal is emitting from inside the heart of the abandoned Kalar Anchorage. This massive facility was once the Byotai Empire's greatest shipyard, but now it lies cold and lifeless. Or does it? Upon arrival Nate runs headlong into the centre of a fierce battle.
On one side are the numerous forces of the insidious Orion Interstellar Empire. On the other, the powerful attack cruisers of the Byotai outlaw, Warlord Katanga. Kalar Anchorage has become a refuge for the lost and the damned. The former facility is populated by displaced people and wounded soldiers that have fought, and lost against Star Empire incursions. As well as the exhausted crews of a number of ships.
Yet the forces of Katanga, though weakened by the fighting, still wish vengeance upon those that seek their utter annihilation. Katanga's desire for further violence may come earlier than expected. An entire fleet along with numerous ground forces has entered the system, and they will not leave until every defender is dead or captured. With no time to fully abandon the station, the preliminary skirmishes erupt into a major battle.
The last stronghold that stands between the Orion Interstellar Empire and the hastily mobilised fleets of the Alliance. The Siege of Kalar has begun.