An awful lot of collateral deaths could have been justified in WWII, especially considering the phenomenal murderousness of the Axis Powers. I don't deny that.
The objection is, that the civilians killed at Hiroshima and Nagasaki were not collateral deaths. These deaths were intended, inasmuch as (1) the US chose to use indiscriminate weapons of mass destruction and (2) the US intended that the psychological effect of a butchery of such magnitude would shock the Japanese High Command.
Who can deny that the atomic bombing of Hiroshima would have been considered a dud, if (by some fluke) only the military targets had been destroyed, and the civilians remained pretty much unscathed?
We must make a distinction between killing, and murder. Killing --- and, realistically speaking, quite a lot of it --- may be justified if, at he same time, we are honestly trying to shield the civilian population as much as possible. As, in fact, we are doing in Iraq, where our military has clearly tried to minimize harm to noncombatants (even under horribly difficult circumstance.)
I salute the US military for this. This is courageous, and honorable, soldiering.
That's my point. Honorable soldiers don't target civilians. George Washington didn't target civilians. Robert E. Lee didn't target civilians.
The indiscriminate killing of civilians is, in fact, prohibited by the U.S. Uniform Code of Military Justice. It's against God's law, international law, and the law of the USA.