It is tough to know what do to with the passing of a man who was an architect of the Vietnam War — and who later expressed remorse for it. Three million Vietnamese died, and 60,000 Americans were killed in combat.
Jonathan Schell’s piece in The Nation on former U.S. Secretary of Defense Robert McNamara is worth reading in its entirety. A snippet:
“As the decades of the twentieth century rolled by, the heaps of corpses towered, ever higher, up to the skies, and now they pile up again in the new century, but how many of those in high office who have made these things happen have ever said, “I made a mistake,” or “I was terribly wrong,” or shed a tear over their actions? I come up with: one, Robert McNamara. I deduce that such acts of repentance are very hard to perform.”
Sunjeev Bery 
The impulse seems to be act first, consider later. Robert Oppenheimer had similar second thoughts after the atom was out of the bag. Learning from history might help.
War mongers will always be with us