The Montagnards were fighting for their 'tribe', not for the Americans. I believe this doesn't count in this context.

The Filipinos come more close, but at least the WW2-period Filipino troops were motivated by a promise of independence and thus again fighting for their people, not really for the Americans AFAIK.
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What's remarkable in the case of U.S. troops is that they don't form U.S.Army units with 80-90% foreigners from the region. It's really not that hard, as evidenced by the ease of how European powers did this during Imperialism times. See the German Askaris; German officers surely had no experience in creating such a force, yet built a formidable one in East Africa with IIRC initially Sudanese warriors.

http://en.wikipedia.org/wiki/Askari#German_colonies

Just imagine; rotation would be limited to about 20% of the total force, deployed U.S. personnel could be cut by two thirds and the actual force available in-theatre would still be larger and have enough boots on the ground to dominate most of the places that are now effectively without Western control.
Well-performing and reliable soldiers could be identified and promoted, with gradual replacement of U.S. troops over the span of maybe six years.


I suspect the U.S. has a misleading perception of the quality of its own troops. Most of their qualities are of little consequence in small wars and other characteristics are outright problematic. This also applies to Western mercenaries.
A critical little bit more optimism about the utility of foreign culture troops (done right, not the ridiculous ANA approach) could serve very well.



hmm, why do I pay attention to it? It's small wars stuff.
The only consequence for great war stuff here is the use of foreign culture troops as manpower akin to the French practice of employing black troops in Europe. The success of this was mixed at best.
We don't need foreign manpower for Europe's security (contrary to hysterical demography doom-sayers) and the Roman experience with culturally foreign auxiliaries in the long term is not a promising example.