Among a set of extractive institutions particularly set up by colonial powers themselves, military conscription has been understudied to this day. In this paper, I attempt to delve deeper into this important historical institution in French West Africa (FWA) during the interwar era (1920-1939). First of all, I find that when the conscription target stipulated by higher colonial officials increased, strikingly the lower district-level authorities were not complying with this figure faithfully, even when they complied, the target increase was only met by a dubious increase in “deemed fit” soldiers in regions where labor constraints were already running high. Such findings point to a more complex French colonial rule in West Africa where authorities were “fighting over” the scarce resource of labor. Secondly, I find that in times of negative income shocks, potential flooding events in tropical regions of FWA made individuals more likely to volunteering into the army and correspondingly, an increase in drought risk in arid Sahel regions of FWA also made the indigenous more likely to present themselves to the military. Both effects point to the fact that the conscription system was being exploited as an informal insurance device by the locals at a time when insurance institutions were lacking and weather-induced negative agricultural income shocks were frequent.