ST,
the situation obviously varied from one recruit to another. But the following mught be typical, based on accounts I've read.
1. Jean is conscripted and reports at depot of Nth regiment. There he undergoes personal training and drill training. He belongs to 2nd company of the 4th Battalion.
2. Jean is ordered along with hundreds of others to march to join his parent regiment campaigning in Spain. He ceases to be in the 2nd Coy of 4th BN, and becomes instead a member of a 'Bataillon de Marche' or route battalion made up of conscripts of several regiments.
3. Half of the guys from the Nth regiment get picked off by other commanders in the way. But Jean makes it.
4. He joins the 1st Company of the 1st Battalion, Nth regiment.
If the entire regiment had been in its depot when jean was conscripted, it is possible that he might have gone to that company and stayed with it on campaign.
regards
EC