Originally Posted by metaphysician
Okay, this is tangential, but. . . what?
No, they did not commit a war crime. They ordered a nuclear strike, under circumstances where it would be entirely reasonable to launch a nuclear strike, and with ( implicitly ) proper authority allowing them to do so.
What about their actions would even slightly constitute a war crime ( as opposed to just questionable judgement, which they certainly were guilty of )?
It is a war crime to use weapons of mass destruction in a populated area. From Wikipedia:
Examples of war crimes include "murder, the ill-treatment or deportation of civilian residents of an occupied territory to slave labor camps," "the murder or ill-treatment of prisoners of war," the killing of prisoners, "the wanton destruction of cities, towns and villages, and any devastation not justified by military, or civilian necessity."
The fact that they thought that it would stave off the Chitauri invasion might be a mitigating factor, but they acted against the advice of their own leader in the field, Fury, who deemed it unwarranted at the time. That falls under the heading of "...the wanton destruction of cities, towns and villages, and any devastation not justified by military, or civilian necessity."
The Council was absolutely wrong, because the Black Widow had found the means to close the portal before they launched the nuke at New York. They panicked and jumped the gun, even though Fury argued with them to allow the team to do its work. The US government must have been just thrilled to watch a nuclear warhead unleashed on its largest city and be powerless to stop it. Millions would have died, and needlessly because they established that no form of energy could stop the Tesseract. And on top of that, they would have destroyed the Earth's one chance to stop the invasion, even as they slaughtered the population of one of humanity's greatest cities.
So yeah, I consider that a war crime. "We were afraid" is no more of an excuse than "I was just following orders." Maria Hill told the Council that SHIELD had kept proof of their actions for that reason: it could potentially be used as leverage.