They have glass jaws and can be taken out with a punch by Will Smith. Aliens are stupid. When one of their fighters approaches the carrier, they don't bother to communicate with the pilot. Aliens are even more stupid. They pursue their targets into canyons walls and closing blast doors.
Aliens are unbelievably stupid.
While unarmed and unarmored, they do things to tick off people with hand guns. Aliens are just too stupid for words to express. Aliens are remarkably inarticulate. If you're President and your administration is faltering, an Alien Invasion might be a good way to boost your ratings in the polls. No need to specify what branch of service.