The humane treatment of surrendered captives, therefore, is a crucial--arguably the crucial--understanding
between adversaries if their conflict is to end in any way other than
with the wholesale slaughter of the losers. It's worth noting, too,
that it is not merely the lives of the losers that are preserved. If
they do not surrender, it may be that they are all killed; but it is
very likely that, in the process, they will also kill some, perhaps
even many, of the eventual victors.
And that is pretty much what Sun Tzu (II.19,20) says:
Treat the captives well, and care for them
This is called "winning a battle and becoming stronger."
And just for emphasis, one ancient Chinese commentator on this passage, Chang Yu, adds:
All the soldiers taken must be cared for with magnanimity and sincerity so that they may be used by us.
You can't gain good intelligence from captives if you brutalize and torture them. Too bad Bush and Cheney failed to heed Sun Tzu...