>>222211
Spread out lighter elements through out the system as pickets and plant a few battleship taskforces in the direction we expect them to come from.
The rest of the ships of the line should take up position around the planet.
Mines will be useless outside of denying low orbit to the nids. Space is just too big.
The plan is to harass the nid fleet as it arrives with lighter elements, try to draw off any parts dumb enough to give chase and hit them with the forward battleship forces. Get them good and paranoid and lure them to advance on the planet in one big dense group for defence against the skirmishers. This should take a week or two before they arrive in orbit and the real battle starts.
As their fleet advances on the planet, have the skirmishers group up in bigger groups and shadow the main nid fleet, picking away at any ships that stray from the main force, while the battleship detachments gather up behind the nid fleet following them into orbit.
As the nids decelerate, to avoid overshooting the planet, have smaller skirmishers pull high speed passes straight through the main swarm, identifying and trying to cripple vessels as they pass through the swarm at speeds high enough that the nid ships have no practical way of fighting back. The damage they can do will be limited, but nid ship with damaged engines will be unable to brake in time and will overshoot the planet, reducing the overall force the nids have, and it will help identify the largest and most dangerous vessels in the fleet. By dropping shrapnel and munitions prior to passing through the fleet, even small ships should be able to inflict some damage against even the largest vessels if they can just hit them, along with anything else that gets caught by all the crap they are dropping in the nid fleets path with a relative velocity in the neighbourhood of 200.000 m/s. The fleets making the high speed passes will take some time turning around and coming back, but will hopefully damage or destroy some of the nid force, forcing them to split forces off to keep the damage ships safe, or leaving them vulnerable to other skirmishers.
The force of battleships will also start decelerating slower than the approaching nid fleet, letting them catch up and overtake the main nid force, but at a slower pace than the smaller fleets and timed to hit the main nid force only a day or two before they hit the orbit. Aiming at the targets identified by earlier high speed passes, their main purpose is to be a big obvious threat coming at the nids, forcing them to pull their heavier ships to the rear of their fleet, or leaving the smaller and weaker ships there exposed, leaving the front of the fleet deprived of heavier ships for the main battle against the main force defending the planet, while disrupting their formations and fleet order.
When the real battle starts, let any nid ships that try to get into a low orbit go there. Our defensive line should be higher giving us more room to manoeuvre, while any nid ship that makes it to low orbit to infect the planet will be caught between our ships and the planets atmosphere with no room to move.
The rest of the fleet should be at least partially depleted and damaged by skirmishing and high speed passes, will engage our main force of heavy hitters in a stand up fight in orbit, while our skirmishers converge on the nid force from all sides and the secondary force of battleships overtaking their fleet from behind should put them in a weakend and battered state, between a hammer and an anvil with the tempting deathtrap of low orbit just behind our fighting line where the nids want to drop their spores as fast as possible.
Ideally, the main force should be arranged like infantry squares in the orbit, concentrated groups of battleships and cruisers that let the nids pass between them, allowing us to fire on them in a crossfire.
Surviving ships play orbital wack-a-mole with any nid forces the planetary garrison find.
Once the main nid fleet is broken, the rest of the battle is going to be easy to win for the ground pounders.
Its only a few slimy genestealers and such, how bad could it be?