> The pogroms are generally thought to have been either organized or at least condoned by the authorities. This view was challenged by Hans Rogger, I. Michael Aronson and John Klier, who couldn't find such sanctions documented in the state archives.

So it's basically one big fat weasel. They can't confirm that authorities officially sanctioned anything and that's where "were behind" comes into existence. Proving that you "weren't behind" is impossible.

However, I can see how, in the absense of documented sanctions, I can call the article's author, Matthew Shaer, a liar for his "undertaken" word.

WRT the article. Half of Vilnus's population was Jews. How on earth could a community fear pogroms when being in such numbers? Might as well be the side doing the pogroming.