The asteroid hitting Earth is often said to have been orchestrated by Federation. This doesn't look like it has much direct support from the movie except for the fact that the Federation is jingoistic and people want to expand into bug territory. However, after the Klendathu massacre, it becomes clear that neither the military nor the people generally believe the bugs to be intelligent; if so, then the Army couldn't have seriously believed that that the Bugs were actually aiming asteroids from half way across the Galaxy. The fact that a large portion of the population could both believe that the bugs are unintelligent and attacking them from across the Galaxy, just shows us how Double Think is in full effect.
In the early battle scenes, we see a lot of bugs with blown off limbs, still fighting. Then there is a break and a short PSA which points out the vulnerable spots on a bug. In the next battle, the bugs fall in droves with blown off vulnerables instead.
Carl controls his pet ferret Cyrano ("Go bug Mom!"):
Carl: I gave him the impression that there's a grub crawling up my mothers leg, he's on a mission to go eat it. Carl's Mom: (banging noises can be heard upstairs) What are you doing?! GET OFF MY LEG!! AWWWW! ...Carl! Johnny: Carl, promise me you won't ever do anything like that to me. Carl: Don't be afraid. Can't do humans... yet.
A funny little scene establishing Carl is psychic, right? Later in the film, Rico - who had just ordered his unit not to go after Carmen, because she was almost certainly dead - is suddenly filled with mysterious certainty that she's alive and down a particular tunnel, going so far as to abandon his unit and mission, disobeying orders. And he finds her, as the audience already knew, in the clutches of the Brain Bug. After the Bug has been captured, Johnny talks to Carl, who talks about how getting the Brain Bug will turn the tide of the war etc... and Johnny, suddenly realising, asks him "It was you, wasn't it? You told me how to find Carmen." Carl basically winks and says "that's classified". Carl didn't know Carmen was alive. He had figured out how to "do humans". He was sending Johnny on a "mission" to find the Bug.