I'm looking for a novel that I think was published before 2006; it was a great read.
From what I can remember there was an aggressor alien species that came to earth and put the human race into something like castes to control them. They gave black people power and made whites more like slaves. This alien race were like giant grasshoppers or bugs and could jump high.
There was another friendly alien race that befriended humans; they were very short and might have been a slave race. Humans taught them military tactics and tech, and both these friendly aliens and humans were able to defeat their mutual enemy.