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https://www.rand.org/pubs/research_briefs/RB10014.html
2019 report from the RAND corporation detailing, amongst other points:
"Providing lethal aid to Ukraine would exploit Russia’s greatest point of external vulnerability. But any increase in U.S. military arms and advice to Ukraine would need to be carefully calibrated to increase the costs to Russia of sustaining its existing commitment without provoking a much wider conflict in which Russia, by reason of proximity, would have significant advantages."
