Scifi Book Help

[Spike88]

When I was younger(somewhere in my teens) I ready a scifi book that I would really like to read again. Only problem is I can't remember the title. Although I do remember some key things that should help identify it:

• It was about a massive alien invasion on earth
• There was a giant mobile artillery cannon that could disguise itself as a mountain via a foam
• The aliens either looked like horses of bugs(I can't remember)
• I think it was published by Baen,
• There were robotic exoskeletons to help soldiers carry large amounts of supplies

For the life of me I can't remember the book, and it's bugging me. I've tried several google keyword searches that have not come up fruitful. I'm hoping someone here has read it or knows a better way to look for it.

Any help would be appreciated.