In 1812, napoleon and 400,000 troops encountered severe difficulties as a result of the ___ used by the russian leader in response to france's invasion.

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.