At the Internet Archive is a document everyone should read: Pocket guide to Germany (1944).
That was handed out to our troops who would be occupying that country after its defeat.
Let me just quote a few passages from the first two pages:
Local customs, especially those touching upon religion, are to be given consideration and respect.
Respect property rights. Vandalism is inexcusable.
Rifling of orchards and fields and unauthorized appropriation of food stores are contemptible and punishable by court martial.
Remember that conquered and occupied nations will be critically short of food. Depriving the people further will create great hardship and in the end will cause conditions that will make your own job a harder one. It is always a strain on our supply lines to feed people of occupied countries. Don’t strain it further.
Don’t belittle or be critical of fighting qualities of former soldiers. By now you will have had a good opportunity to judge just how good a fighting man the enemy is. The point is, we don’t like to kick people when they are down.
Boldfaced emphasis added by me.
These words weren’t written for effect or for public relations.
That was the ethos of America once upon a time.
Contrast that to the wide-ranging brutality in Iraq, in Afghanistan, and then go see the many war porn videos on YouTube.
See for yourself how we create hatred today.
An army of principles will penetrate where an army of soldiers can not; it will succeed, where diplomatic management will fail; it is neither the Rhine, the Channel, nor the Ocean, that can arrest its progress; it will march on the horizon of the world and it will conquer.
Principles are transmitted by people.