No main purpose was fur trading
Scorched Earth policy. The Russians burned whatever they couldn't take with them. In that period, lots of supplies were gained through scavenging and taking from the locals, but with everything destroyed, the French had no supplies bar what was being sent to them, but the further into Russia they got, the longer it took for supplies to catch up.<span />
Since i can’t see the timeline i’m just gonna assume that it’s referring to Pax Romana, since the rest of those things were not as long as Pax Romana
