The movie point blank says the bugs attacked first and that it’s a colonization species that just hurls meteor filled bugs randomly into space in order to try and find new planets to colonize.
Also, when the “main” character in the movie (Rico) is in basic training and about to quit the military, a bug meteor impacts the earth, taking out an entire city, and killing his parents, so the bugs were most definitely attacking humanity, and earth directly.
The movie also ends on a high note, making it seem like they learned some very important information by capturing one of the until then unknown bugs that was able to think and direct all the mindless bugs. So while the war will go on, it leaves the viewer to think that humanity was making progress towards a victory. The movie also marked the first time that humanity actually went to the bug home planet and “took the war to them”.