Every six months the Director of National Intelligence must report, by law, how many terrorists formerly detained at Guantanamo Bay have resumed terrorist activities. The last report pegged the recidivism rate at 30.1 percent —124 confirmed as once again engaged in terrorism, 96 suspected of it.

That report was issued on Jan. 15. The next should be published soon. As we brace for those new numbers, it may be useful to review some background information.