I remember seeing a movie called, "The 300", that was about a small army of Spartans fighting to the death,  holding off the great Persian Army in battle long enough for the rest of the Grecian troops to escape.  Because the Greek city-states practiced a form of early democracy and had some form of representative government and were independent of an all powerful ruler, they may have had a psychological advantage to battling for their way off life,  compared to the Persians who were ruled with an iron fist in the form of a supreme, god-like ruler.  In the modern era we may have comparisons to the democratic government led troops of WW2,  defeating the the aristocratic, fascist, and totalitarian ruled armies,  for nothing less than preserving their democratic way of life.