Final answer:
The majority of Napoleon's soldiers during the Russian campaign came from non-French territories, with a significant number from Italy and Germany, and many being under-trained recruits.
Step-by-step explanation:
The majority of Napoleon's soldiers during the campaign against Russia were drawn from territories other than France. While many of Napoleon's most experienced troops were engaged in Spain, his "Grand Army" consisted significantly of recruits from non-French territories, predominantly Italy and Germany.
Moreover, many within this army were inexperienced recruits with insufficient training. This lack of experience, combined with the harsh conditions and the scorched earth policy employed by the Russians, led to disastrous consequences for the French forces, culminating in a catastrophic retreat with high casualties.