The principle is called Just War. It is a derivative of the principles put forth by St. Augustine.
en.m.wikipedia.org
It is an ethical checklist of sorts to insure your actions are necessary and honorable.
One part of being honorable is honesty. Let’s say you and I are neighbors and we have an argument. After a short while we decide to talk and at the conclusion of the discussion we shake and declare everything is good.
We have disagreed over where the property line is. We discuss it and agree to let a survey determine the truth. We go to an outside party.
Afterwards I call the cops and swear you are dealing drugs and there are underage kids in there. My actions are unjust. My actions are dishonorable. I am dishonest in this scenario.
Such things end up in the news as a bad neighbor. Most everyone would agree that in that scenario I was an asshole. Any excuses I offer later would be ignored or laughed at.
Russia is not conducting a Just War. America was wrong. There were no WMD’s in Iraq. The evidence could be interpreted as Iraq having them. But they did not. And America suffered a black eye for being wrong. However America did set out to demonstrate that the war would be just.
Russia by contrast set out to lie. And they lied. They lied the day before the actual invasion. They announced it after the reports from Ukraine hit the news wires.
Russia’s actions were so dishonorable that even Switzerland who has spent centuries being Neutral in every conflict took sides against Russia. Think about that for just a moment.
There is no comparison between the American invasion of Iraq and Russia in Ukraine. None. And any effort to do so is at best disingenuous. At worst another flat out lie.
And finally. The difference between a lie and a mistake. Let’s say you are being questioned by Police. They ask if you saw Bob Wednesday Evening. You think and say yes. You saw him that evening. It turns out that it was Tuesday you saw him. You confused the days. You made a mistake. Mistakes are human. We all make them. If on the other hand you know you didn’t see him on Wednesday but you say you did. That is a lie. When you knowingly present false information.
Russia lied. America was mistaken.