As a side note, an incredible amount of modern military terminology and rank titles (at least in English) can trace their ancestry directly back to the Middle Ages. "Colonel" was apparently originally a Late Medieval Spanish term for what IIRC seemed to be a big-time condottiere, for example.
Good thinking heh, but "colonel" comes from the latin equivalent of "column", columna if I'm not mistaken. Maybe the word you 're looking for is caudillo - ofcourse the word came to encompass many extra meanings over the years.