try reading the article from the above link, it is huge yearly document of Nepal Army but it has many answers of your questions. there are many reasons regarding nepal gov allowing her young citizens to get recruited in foreign army. in first and second world war aprox 400,000 gurkhas voluntereed for the great war and nepal gov provided the assistance of nepal army itself primarily for support role. well, first is economic factor, rana government were receiving 5 pounds per gurkha recruited in great wars and yearly royalties. another reason could be to strenghthen the relationship between two nations after anglo nepal war which was given more priority in rana regime. many gurkhas chose to stay in some foreign countries when they were in a war, many r still living in assam, burma, malaysia. recently malaysian gov even honored this fine men by giving land n house for thier service in quelling communist rebels. my grandfather marched in the street of japan after allied victory over japanese in WW2