According to a 2015 WIN/Gallup International global survey, which asked respondents in 64 countries whether they would be willing to fight for their country in a war, Japan had the fewest people willing to go to war (11%) while Morocco and Fiji tied for the highest (94%). The U.S. and Russia were at 44% and 59% respectively, while rising powers China and India were at 71% and 75% respectively.
Regionally, Europe had fewest people willing to fight a war for their country while Asia had the most.
A total of 62,398 individuals were surveyed globally between September and December of 2014, with roughly 1,000 men and women serving a representative sample for each country. Interviews were conducted in person, by phone, or online. I’d be curious to know how much the results have changed since 2014.
Of course, a willingness to go to war in the abstract does not necessarily mean that one will answer the call of war if it actually comes. I think Americans in particular are far more gung ho about war in theory — from which the vast majority are far removed from experientially — than in practice. (Tellingly, a lot of the higher-ranking countries in terms of willingness to go to war — such as Finland, Russia, and Turkey — have compulsory military service.)