(The Wall Street Journal) — ‘The Dictator’s Playbook” (Wednesdays, 10 p.m., PBS) looks at six of the 20th century’s most infamous despots with an eye to the characteristics common to them—the premise of the series being that dictators learn from one another.

It’s an absorbing, richly documented work. If the series has a flaw, it’s the frequency of the academic commentaries—messages that expend a good deal of time in emphatic explanations of the obvious.