So that one Flashback scene from X-Men Origins: Wolverine depicting Logan and Victor fighting in Vietnam. How that completely was screwed over (ish) with days of Future Past, William Stryker not recognising Logan at the Paris Peace accords meaning he hadn't recruited either Logan or Victor for Team X yet, but Victor still needs to kill his commanding officer in Vietnam, yet all American Troops will be out of Vietnam quickly following the Paris Peace accords. Even in the movie, following the scene where Logan wakes up with "Gwen", the "Bosses Daughter" there's that quote in the movie:
"Today, the 18th MP Brigade is departing from Saigon, marking the last American troops to leave Vietnam. And effectively ending the war."
So how does this make any sense in the original timeline? I could be wrong here, but I think I've solved it. Logan and Victor are Canadian. So they were involved in Operation Gallant http://www.cmp-cpm.forces.gc.ca/dhh-dhp/od-bdo/di-ri-eng.asp?IntlOpId=65&CdnOpId=77
Canada was involved from 29/01/1973 - 31/07/1973 joining Poland, Hungary and Indonesia. Although the other countries were involved past longer than Canada was.
The goal was "To provide a neutral party to investigate compliance and to conduct monitor the enforcement of the terms of the Paris Peace Agreement"
In the international section we are told "The same was true of its cease-fire monitoring role: in the first six months there were at least 18,000 reported violations, causing 76,000 casualties, just four thousand casualties short of the total recorded in the last six months of actual fighting."
If Logan and Victor were involved In monitoring and enforcing the Paris Peace Agreement, by the sounds of it the seven months Canada was involved here would have given them plenty of opportunities for action like we saw depicted on screen to neutralise. Now I'm no expert on American Vietnam uniforms vs Canadian Vietnam uniforms, but a quick Google search to me and they look indistinguishable, and I can't see any markings or symbols or flags revisiting the scene that identifies the military personnel as US Army over Canadian. There are some shoulder shield symbols in the firing Squad scene but these are upside down to the ones seen In the US military uniforms for Vietnam I've come across (and don't appear to have gold V stripes either).
What's more, there was one Canadian casualty during their time there, on April 7th Captain C.E. Laviolette and 8 non Canadians were shot down from their Helicopter. But in the X-Men universe, what's to say the one casualty (the Canadian captain) even died in the helicopter Crash? he could have been the "superior officer" killed by Victor in the fictional version of events, and as a cover up it was just reported that he died in the conflict with the shot down helicopter that had happened earlier in the day, that Victor and Logan were sent out to investigate. The Canadian military certainly wouldn't want it to get out that one of their own had been killed by another Canadian, and a mutant at that.
And at least according to this https://www.cbc.ca/news/canada/british-columbia/lost-to-history-the-canadians-who-fought-in-vietnam-1.3304440
"it was actually illegal for him [a Canadian who wanted to fight with the US military in Vietnam] to fight in a war that didn't formally involve Canada." So this could explain why Logan and Victor were separated in early 1973. Victor wouldn't care if it was legal or illegal for him to fight, so he would have joined the US illegally in Vietnam, but Logan, might have cared just that little bit more than Victor not to get involved, hence he was with Gwen, the bosses daughter. However, when it was time for Operation Gallant after the Paris Peace accords, then Logan would go and get involved and be reunited with Victor who would no doubt do anything he could to continue fighting. With the Canadian casualty occurring on April 7th, that's plenty of time for Logans hair to grow from the length we see in days of Future Past original timeline to the length we see in this Vietnam Flashback as well (3 months).
What do we think? Is this a suitable solution finally? Am I missing something crucial? I'm from the UK so my understanding of US and Canadian military history is that of an outsider.