Deep Strike — Rick Shelley

Finally reaching the stars, humanity joined the Alliance of Light--a coalition of alien worlds dedicated to exploring the universe and facing its dangers together. A new military regiment, made of soldiers from every planet in the Alliance, has already won its first victory against the Ilion Federation...

Having proved themselves with the liberation of a Federation-held planet, the First Combined Regiment recuperates on Earth. It isn't long before they're back to basic training--and it's Sergeant Bart "Dragon" Drak's job to ensure that the varied alien species in his squad learn to integrate without tension and function as a team.

Now, Drak must lead that team in a strike against the heart of the enemy when the regiment is ordered to invade the world of Olviat, and occupy it. But if this attempt to take the initiative in the war fails, it could shatter the Alliance...