They are there. Go to the Planetary invasion line. Once you  pass it you will have to chose one of three 'types' of invasion techniques (Planetary bombardment, Infomation conversion, or Biological warefare). Then you research some more soldiering, then you get to another choice, (Tidal invasion or Core Detonation, both from GCII) and then two more Soldier improvement techs. 

I go Bio every time but that is me. Many folks love Information warfare. In all cases you still need 'Boots on the ground' and need to send in a troop transport with warm bodies.