So that it is more clear, here’s an account of who is mistaken about what.

1. For a long time many people thought that Jan Karski visited Nazi extermination camp Belzec during the war and brought news about that to the Allies. He basically wrote about this in his 1944 book, and the story “stuck” for many years. (So Obama is incorrect that Karski waited for decades before telling his story.)

2. Later research by Karski-approved biographers showed that he hadn’t really visited extermination camp Belzec. Whether he was sincerely mistaken, or intentionally embellished his account - decide for yourself; but the biography of Karski (that he approved) states that he actually visited the transit camp Izbica. (Search for “Izbica” in this thread, I’ve already posted some information about this, including the quote from the book.) So Obama and numerous of his critics are incorrect in saying that Karski visited a “death camp” since Karski never visited a death camp. An earlier White House press-release actually makes the correct claim about Karski visiting a transit camp, not a death camp.

3. In any case, Belzec was not a Polish death camp, but a Nazi death camp or a German death camp, so Obama was indeed incorrect in calling it that.

4. In any case, the events concern Karski sneaking into sealed off locations are about Belzec or Izbica, not Auschwitz, so Frum is incorrect in bringing up Auschwitz when it has no relation to Karski’s mission.