Total available manpower proves critical in a drawn out conflict. For the purposes of the GFP ranking, a nation showcasing an inherently large population (as in China or India) has the theoretical benefit of committing more souls to the fighting.
Available Military Manpower data through 2015.
Sources: CIA.gov, CIA World Factbook, wikipedia.com, public domain print and media sources and user contributions. Some values may be estimated when official sources are lacking.