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True, but the other two circumstances were very different.
Obama fired McChrystal for criticizing him of poor judgement in a Rolling Stone article.
https://www.bbc.com/news/10395402
Truman fired McArthur for failure to follow directions, prolonging the Korean War.
https://www.trumanlibrary.gov/education/presidential-inquiries/firing-macarthur
It’s far more likely Trump would use the National Guard, having already leveraged William Barr’s loophole to deploy them against citizens in DC and Portland.
https://www.nbcnews.com/think/opinion/trump-barr-used-loophole-deploy-national-guard-u-s-cities-ncna1236034