I'm almost done with the book of Deuteronomy, and I've really enjoyed it so far. Genesis used to be my favorite book in the Old Testament, but this time reading through the Old Testament I think that Deuteronomy is. At least it is so far. Here is a comment on chapter 20 from Rousas John Rushdoony in his book The Institutes of Biblical Law:
"Another general principle appears from this law ... that it is not enough for the cause to be holy; not only the cause, but the people of the cause, must be holy, both spiritually and physically."
I just thought that was a very profound statement, and it shows that the most important war should be against evil in ourselves. The best and most effective restraint is self-restraint. This also reminds me of a quote that read a while ago in Susan Wise Bauer's book, The Story of the World vol. 4. She was discussing the pattern of the last couple hundred years where, in different place all over the world, one group overthrows a tyrant only to become a tyrant itself.
"Revolution shatters the structures; but the men who build the next set of structures haven't conquered the evil that lives in their own hearts. The history of the twentieth century is, again and again, the story of men who fight against tyrants, win the battle, and then are overwhelmed by the unconquered tyranny in their own souls."
If the people of the cause are trying to be holy and honest with God and man, this probably wouldn't ever happen.