This is how Ender thinks the humans looked fighting against the buggers during the Second Invasion – the humans didn’t do so well. It's an interesting comparison Ender is making. According to this, children are weak and don’t win against grown-ups. The rest of the book might make us reconsider that thought, though. One example is when the adults at the Battle School come up with unfair situations for Ender to battle through. Remember when Ender tells Anderson that he (the child) has beaten him (the adult)? (It’s 12.171, in case you wanted a big fat hint.)