I am still working my way through this thread (and making a list of points to raise!) but I do have one thing to say now:
Anvil exist, so presumably they have a purpose.
Is that purpose to occupy things that cannot be bombarded - either due to fragility, importance, or possession potent ground-to-space defences?
I boggle at the idea that ground based anti-Hammer weaponry cannot defeat Hammer. Coastal fortresses are too cool a “ye olde warfare” trope to ignore I think. Besides, now Anvil lords can have ‘castles’ with high ‘towers’ (massive q-beam emplacements); possibly even protected by Imperial-style (from the Foundation series) ground-based forcefields?
First of all, as is evidenced in the Faith Conquers book, hammer assets aren’t as easily available as anvil troops. Hammers are expensive, and have a lot of tech that’s hard to come up with. Each ship is built to order, from what I understand, and not created in a factory somewhere. So there are lots of fights where they’re just not available, and then you need the anvil.
Second reason is simple - buildings. If you want to occupy a complex or a building, you have to have foot soldiers do it. Same goes for cities. Sure, you can blast the city into bits with orbital weaponry, but that kind of collateral damage is not acceptable.
Finally, fortifications exist in places difficult to blow up from orbit - underground, namely. Again, if the hammer wants to nuke the site from orbit (it’s the only way to be sure, after all) that’s fine - but even a nuke can only penetrate so deep, and then there are all the pesky environmentalists to deal with.