The Reefs Of Time — John Costello

The anasan explorers on the starship Anavasan had failed to find the advanced civilizsation they had expected on the second planet of the near-by star; their home world was now dead on the radio spectrum; and worse. the Sardu theocratic fascists had staged a coup and taken control of the ship and the colony. Their only hope lay in contacting the local bi-pedal primitives, but before the primitives could be any help they would have to end a war of their own
--World War Two.