European territory annexed, democracies stunned into paralysis and Nazi salutes -- Donald Trump's shock re-engagement with Russia looms over a geopolitical landscape that, for many, has dangerous parallels with the rise of fascism and the West's feeble response in the 1930s. Though a century separates the two eras, historians on both sides of the Atlantic are plumbing the depths of Trump's break with decades of US and European doctrine, at a time of military escalation worldwide.