[Strategia_In_Ultima]

There'll be anti-planet weapons, but they'll be expensive and huge. Population will have high amounts of hitpoints, so you may have obliterated every troop, weapons platform and facility on the planet, but it's going to take you quite some time to kill every last inhabitant of the planet. Ground combat is difficult and grueling, but nuking 'em is expensive and very time-consuming. With a dedicated fleet you'll be able to pull it off, but it'll be one hell of an expense.

By the way, why the focus on the ground combat part?