19:54 Nov 2, 2010 

When conscription was still in force in France, you could enroll before service time for a préparation militaire (terre (PMT), parachutiste (PMP), supérieure (PMS) or PME (élémentaire or encadrement). It meant training for a couple of weeks or more depending on the "préparation" chosen. You learned about weapons, crawling, jumping, digging holes, oh, and making your beds "au carré", besides a lot of exercise from very early in the morning. The basic warfare stuff.
So this officer was responsible for training those conscripts-to-be.
The advantage, besides a free haircut, was to get a slightly better pay more quickly at conscription time or be in specific regiments (paratroopers for PMP), and PMS certificate holders fast-tracked to become an officer during conscription (with all related benefits).