>>95938542>Going back to 40k planetary defenses, the idea that people can land transports but can't bombard the place with warships doesn't really make sense1 - important stuff under shields
2 - outside shields is empty land or stuff not worth bombing (except maybe some AA guns and other defenses)
3 - park big ships outside range of planet's big guns (if the planet even has any)
4 - send waves of landers to land in unshielded areas (anti-air/lander defenses in many sci-fi/science fantasy setting tend to be pretty shit and short ranged, particularly in 40k, though you will lose some landers if there is enough of them)
5 - troops fight their way to get under shields and eventually disable them
Fortifying every inch of a planet is possible but most developed worlds like hive worlds cluster key infrastructure and main defenses in a few locations (hives), which basically forces opponents to commit to a ground invasion instead of just bombing from orbit if all they want to do is destroy key assets rather than take the planet.
>>95938568But yeah, a lot of times the fight is to capture the entire planet relatively intact.