I'm not sure they qualify as that, but there are certainly people that believe that Robert McNamara was a war criminal [0]:
"""
“We burned to death 100,000 Japanese civilians in Tokyo — men, women and children,” Mr. McNamara recalled; some 900,000 Japanese civilians died in all. “LeMay said, ‘If we’d lost the war, we’d all have been prosecuted as war criminals.’ And I think he’s right. He — and I’d say I — were behaving as war criminals.”
“What makes it immoral if you lose and not immoral if you win?” he asked. He found the question impossible to answer.
"""
IIRC both Hiroshima and Nagasaki were chosen because it would hurt japanese military the most. Back in those days a plenty of civilians died anyway during regular bomb raids.
But yeah, to some extent is probably was a terrorist attack.
That's the excuse that was given, but the regular bombings had been systematically doing precision raids during the day and indiscriminate firebombing during the night for months at that time. They were running out of significant cities to bomb well before Hiroshima, to the point where they'd started firebombing much smaller cities with no air defences or military presence to speak of as well - some of which were almost entirely obliterated.
""" “We burned to death 100,000 Japanese civilians in Tokyo — men, women and children,” Mr. McNamara recalled; some 900,000 Japanese civilians died in all. “LeMay said, ‘If we’d lost the war, we’d all have been prosecuted as war criminals.’ And I think he’s right. He — and I’d say I — were behaving as war criminals.”
“What makes it immoral if you lose and not immoral if you win?” he asked. He found the question impossible to answer. """
[0] http://www.nytimes.com/2009/07/07/us/07mcnamara.html?pagewan...