Ultimately, every planetary invasion boils down to a political op. You wouldn't have launched the war in the first place if you didn't want control of the planet, it's resources, or at the very least the space lane. Through force, fraud or diplomacy, an invader must bend the population to its will.
Agreed & force is merely a hightened level of political negotiating.
Most planets would be bought into line through the existing leadership via negotiations, coersion & regime change in that order. However if regime change is required an invasion force has to achieve two goals:
1. remove & replace the current leadership
2. win over the population to follow the new leaders
To this end, some of the rather 'blunt' approaches that first come to mind are counter-productive. Don't use terror tactics on your new neighbour & ally.
Taking the planet after the initial orbital/coacc battle is won will involve 'Node Warfare'. Nodes being the critical physical points every high tech civilisation has. Population, Government, Religious, Energy, Transport hubs, Comms, Spaceports, etc. Capturing the most important nodes for this world effectively negates the defenders use of Meson or Nuke armaments against the occupiers. To dislodge the invaders, the defenders will have to come out & play, however that is unlikely to happen, instead there will be a strong defence of the node followed by a controlled withdrawal if neccesary.
In using Node warfare the invaders will have effective control of the planet without requiring millions of troops.
The defenders tactics in the first phase, will be to resist strongly then withdraw, Meson & Missile sites should be used extensively to increase the cost to the invaders whilst they are available, while SDB's and the like should be kept hidden. Inevitably someone will talk under interrogation and even the Meson sites will be neutralised. In the second phase, invader occupation, the defenders wait for the invading Fleet to move on. This may be within days or weeks of the initial invasion and will compromise the occupiers available support. At this point, combined attacks to re-capture nodes whilst SBD's distract the occupiers support craft become potentially viable.
In effect, the defence plays for time. Time will lead the invader to redeploy his initial Fleet to new battle zones, leaving behind the invading force and support craft, perhaps including a Cruiser or a couple of Destroyers. Eventually even these will get called away.
The offence plays for quick regime change and population acceptance. Psy Ops will play a premium role, as will the occupation and efficient running of the nodes captured. Propaganda along the lines of "Imperium run electricity at half price, profiting the people!", etc will win over large swathes at relatively cheap short term cost to the Imperium. The defence will attempt sabotage and provoke occupier atrocities which will counter the propaganda, while the occupier will in turn try to portray the defence as irrelevent, dangerous and a hinderance to the populations lives under new leadership. Simultaniously the defence leadership will be the attention of negotiation, coersion & regime change.
The winner will be the side to win over the population in support of thier leadership.
Cheers!
Matt
