Ignatius: The U.S. is finally catching up to the domestic terrorism threat

It’s often said that soldiers don’t hear the mortar round hurtling toward them until it explodes. For most Americans, that was true with the insurgency that detonated at the U.S. Capitol on Jan. 6. We should have seen it coming: Intelligence reports from local police and the FBI describe a wave of domestic terrorism building through the summer and fall as the United States headed toward the November presidential election. But as is so often the case, law enforcement agencies didn’t take decisive action until too late.