The story involves a famed mercenary general that will only work for those clients he deems "worthy." In reality he is working towards galactic peace using his army as a tool to reshape interstellar relations in to a more peaceful configuration. A supercomputer helps him decide which wars to fight/win to achieve that goal. A woman is involved as a potential wife as well.
This is likely an older story (1940s?) as I read it in the 1970s.