What may be most disturbing is not that Mr. Obama was wrong, but that apparently he was right. By all accounts so far, the government had no concrete intelligence warning of the assaulton Wednesday that killed 14 people in San Bernardino, Calif.

Swift, ruthless and deadly, the attack appeared to reflect an evolution of the terrorist threat that Mr. Obama and federal officials have long dreaded: homegrown, self-radicalized individuals operating undetected before striking one of many soft targets that can never be fully protected in a country as sprawling as the United States.

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"We have moved to an entirely new phase in the global terrorist threat and in our homeland security efforts," Jeh Johnson, the secretary of Homeland Security, said in an interview on Saturday. Terrorists have "in effect outsourced attempts to attack our homeland. We've seen this not just here but in other places. This requires a whole new approach, in my view."