EXPEDITIONARY FORCE by Craig Alanson
Joe Bishop is a young army grunt from Maine. His age and inexperience are about to be tested as the earth is invaded by hamster-like aliens known as the Ruhar. After forming an alliance with the lizard-like Kristang to defeat them, the humans join a galactic war to track them down and destroy the Ruhar in space.
The first Expeditionary Force is created.
Joe finds himself leading 70 men in an epic mission around the galaxy. He’s accompanied by Skippy, a belligerent, snarky but ultra-intelligent sentient, who also looks like a beer can. Skippy might be able to help Joe on his mission and so humans everywhere in their hour of need.