Alright, then for this battle, clearly, careful planning is key. If I possess that knowledge it is obvious I am keeping a close eye on them and thus have a somewhat experienced band of spies. If I knew they were coming to my planet/base to steal my supplies, and I knew they were wise and powerful, my greatest weapon would be surprise. Possessing knowledge they do not know I have is a very strong advantage. I would try my hardest to not alert the Alliance, but carefully assemble forces discreetly close to their base. I would take great care to carefully move some crops off-planet to other facilities. I wouldn't move it all because I know that would tip-off the alliance.
This maneuver relies on the idea that the Alliance will take my men seriously and not underestimate them. When they send their forces, which will hopefully be substantial because they won't underestimate me, and go to my base, I would immediately launch a surprise attack when their forces are half-way to my base or more and there-fore cannot get back to base very quickly.
I would stick with my earlier strategy of taking the ground first. Using all guerilla ground forces at my disposal and using quick landing crafts to get them on surface, I would immediately try to take over their defense grid, or at least a section of it. Striking hard and fast with the element of surprise, I would try to take their defense grid from them. If this manuever was a success, I would land all ground forces as well as my space fleet in this section. With their defense grid I'd be using their own weapons against any craft that tries to land behind me as well as their fleet that is inevitably returning from the siege of my base, who have heard about to attack.
With this strong foot hold I would continue the tactic, block by block, section by section, until I could control the whole planet. Of course, the desired goal would be to control it BEFORE their fleet comes back, but that is an unlikely scenario.
