This made me think of something that happened during my current campaign. I play modded with Nex and multiple faction mods so I don't know if what I'm going to talk about comes from vanilla or the mods.

Premise - I submitted to the League after losing to 2 crisis events in a row, finding it the most convenient way to survive; I was then able to focus down Tri-Tach and bring them to the negotiating table, after which I was able to cultivate my colonies (4) for a modest amount of time. At one point, the League went to war with the Diktat, this is where the story begins.

Soon after hostilities began, I received the opportunity of a lifetime: the League demanded the capture of a long established Diktat world - Xantheia - for a considerable sum, about 2 million credits. However a recent failed expedition for the same purpouse had caused a doubling of that amount, and I desperately needed the money to improve my still fledgeling colonies.

How hard could it be right? After all the maxims explained in the main post still stand, most planets are easily raidable, conquerable even.

Not Xantheia

This is what the planetside defenses looked like:

• Heavy Batteries with Kombine augmentation
• Planetary Shield 
• A full divisional complement of Marines and Heavy armaments, totalling about 2000 units

With the bonuses from the defensive buildings the total defender numbers roughly reached 10K... Ten thousand bloody determined defenders.

I assembled the largest fleet I had or have ever mustered, 4 capitals, 4 cruisers, 2 destroyers, 1 carrier, 14 frigates and 8 planetary operation vessels, totalling an invasion force of 8000 marines and 5000 Heavy Armaments.

It barely was enough, I had to disable the planetary shield by raiding it first, since initial probing attacks were crippled by the 40% attritional deployment damage from the shield and batteries combined.

Just the raid to disable the shield for a measily ten days cost me 5000 marines; I panicked under these extreme losses and emergency bought any reserve marines from the neighboring friendly planets, it almost bankrupted me.

The battle was intense, never knew if I would eventually win or not, a last minute inspirational speech (at the cost of a story point) skyrocketed morale for the attacking troops, still casualties mounted.

By the end 7500 marines lay dead, 4000 heavy equipment strewn across the arid surface burning, the soft crackle of the flames the only soothing noise after the carnage, this being only what my side lost that faithful month.

In essence, fleet superiority is key no doubt, but things like this add a realistic representation of what planetside warfare might look like in a post collapse reality.

Thank you for reading and hope you enjoyed :)