US B-29 Superfortress dropped a atomic bomb "Fat Man" on Nagasaki on August 9, 1945, killing up to 80,000, injuring several times more people, and destroying the entire Japanese city.

For 70 years now, the anniversaries of the Hiroshima and Nagasaki bombings have occasioned debate on whether or not those bombings were necessary, and whether or not they were justifiable.

Many World War II veterans — and others — stand on simple necessity to justify the bombings. A US invasion of Japan's home islands, they argue, would have entailed a million or more US military casualties, and even more Japanese civilian casualties than are attributed to the atomic attacks.

The argument is facially persuasive. As of August 1945, my grandfather and my wife's father were both serving in the US Navy in the Pacific. There certainly existed a non-trivial likelihood that either or both of them would have died in subsequent battles had the war not ended. For obvious reasons, we're grateful they came home alive.

The persuasiveness of the argument fades when we consider the facts: Conditional surrender had been on offer since late 1944, the condition being that Emperor Hirohito remain on the throne. The US fought two of the war's bloodiest battles — Iwo Jima and Okinawa, at a cost of tens of thousands of Americans killed — then unleashed Little Boy and Fat Man on Japan's civilian population, rather than accept that condition. But once the war was over, Hirohito was allowed to remain Emperor.

That aside, words mean things, and neither our happiness at our ancestors' survival nor any military argument for insisting on unconditional surrender and dropping atomic bombs to get it changes the character of what happened at Hiroshima and Nagasaki.

Terrorism, per WordNet, is "the calculated use of violence (or the threat of violence) against civilians in order to attain goals that are political or religious or ideological in nature." The Hiroshima and Nagasaki bombings meet that definition in spades.

US President Harry S. Truman ordered, consciously and with premeditation, the murder of somewhere between 100,000 and 250,000 civilians in pursuit of his political goal of unconditional Japanese surrender.

Whether or not an act constitutes terrorism doesn't depend on whether or not its goals are laudable. Every terrorist and supporter of terrorism in history, save a handful of thorough nihilists, has justified his or her atrocities on the basis of the desired outcomes, claiming that a few innocent lives sacrificed now means more innocent lives saved later.

But innocent lives are not ours to sacrifice. Murder is murder and terrorism is terrorism, no matter what nationalist or patriotic colors we wrap them up in and no matter what ribbon of "necessity" we stick atop them.

Even if we accept the "necessity" argument for the murders at Hiroshima and Nagasaki, they remain something to regret and to mourn, not something to justify or to celebrate.