Joe: No, actually, I can’t verify it, and neither can you. In fact, the more I think about that story, the more preposterous it sounds. First of all, of all the brisim that must have taken place over the years since 1948, at which, undoubtedly, many anti-Zionist gedolim were present, we’ve never heard of the Brisker Rebbe saying tachanun, Satmar Rebbe, Rav Amram Blau, Rav Shach, etc. Only this one story.
Second, it’s part of a whole section of not being mechadesh a ta’anis on 5 iyar and not be mechadesh a ta’anis for the victims of the holocaust. So to say that he decided to declare some sort of “eis la’asos” in this case seems fanciful.