Just watched a mini-series about Wellingtons campaign in the penninsula and basically soldiers were portrayed as absolutely brutal. Being very interested in history I already read a bit about the time and the conflict, but for some reason never looked at this question. I am aware that the rules of war were quite different from ours today and that the concept of moral&violence was a different one.
What i am looking for is information about what would in their own society and time have been serious crimes. What was the normal/accepted behaviour of individual soldiers towards civilians of either allied oder enemy nationality? How was rape perceived or the killing of children and babies? Was there a noteable difference between the armies of the countries involved? Or maybe even between regiments, commanders, type of troops (dragoons, rifles, line, hussars...)?
On a general basis it was usually, neutral I would say.
Looting was usually the worst that would happen and that could be common place. Blucher of Prussia encouraged his men to loot anywhere that wasn't Prussia proper. The Cossacks of Russia were notorious pillagers and looters, causing ruckus and mayhem from the Russian frontier all the way to Paris. The French looted quite a lot in Northern Italy, especially in Napoleon's absence when he was in Egypt. Napoleon himself disapproved of looting but he did collect art from defeated enemies on behalf of the Directory's orders. I believe he continued doing that as Emperor.
Whenever morale broke down it would be difficult to reign in the men from looting, but the only occasions where things got worse than that, that I have personally read about, are in Spain and Russia. Spain was a bloody guerrilla war and both sides committed atrocities against each other, the Spanish massacring French soldiers and the French sought bloody retribution.
In Russia, the civilians themselves brutally murdered many French soldiers under the pretense of offering shelter and food. There is one account of a line of French soldiers with their heads on a log, as Russian civilians with branches and clubs ran down the line bashing their brains out.
During a few occasions in the Peninsular war, British morale broke down and the men looted and pillaged with the worst of them. Wellington's famous remark of his men being "the scum of the Earth" was the result of one such scenario.
The Peninsular war was really the location of the worst crimes, but outside of that it was typically just looting, usually under specific commanders who enjoyed it. The French Marshal Davout for instance, had a famously disciplined command and forbade any looting by his men.