Army reports from the time showed that lower caliber handguns were not particularly successful in stopping Moro combatants. The .45 has considerably more 'stopping power', and was much more effective.
The Phillipine Insurrection was a very bloody affair. The local Moros noted that "Attacking an American is like setting off one firecracker in a link. They'll all go off if you attack one." The culture down there is unbelievably violent, the eradication of slavery a very recent affair, and they are known in the region as pirates, criminals, and bullies.
Yes- not a very admirable people from all I have heard- bullies- murderers- pirates- and thieves.
Amazing the parallels between the dawn of the 20th Century and the dawn of the 21st. Well, except for the fact we haven't decided to build a canal anywhere or send the Great White Fleet around the world...very tough fighting for our Marines/soldiers for several years in the Philippines.