The Soviet invasion was an act of terrorism. It was not justified in any way. It was illegitimate violence for a political goal. Terrorism.
South Vietnam: No invasion. The terrorism was committed by the North Vietnamese. Things like cutting off the arms of anyone with a smallpox vaccination scar to make people afraid to accept anything from the West.
You need to learn a little history.
In the early 1960's the US invaded South Vietnam and killed South Vietnamese.
The US went to war against the South, not the North.
The US bombed the North. The US never invaded the North.
It bombed and invaded the South. because the people in the South wanted a united Vietnam as much as the people in the North.
The US also bombed Cambodia and Laos. More massive terrorism.
Iraq: Saddam tried to keep WMD that he had agreed to destroy. It doesn't matter that the weapons were actually phantoms, Saddam believed they were real and was trying to hide them.
No WMD were found in Iraq.
But of course only children could still believe the attack had anything to do with WMD.
The people, and it was a small group of people, who lied to the nation to drive the nation to war had wanted to invade Iraq for over a decade before 911.
They were psychopaths who talked about a US century.
Their sick plan included a lot of killing. Iraq was just the start.
That went so badly these scum have scattered.