Last line of defense, only line of defense in some instances.
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Fox News columnist and author John R. Lott argued on Monday that armed citizens are the last line of defense against individual, ISIS-inspired or ISIS-type lone wolf actions such as the recent one in Ottawa, Canada.

Lott provides a sampling of recent attacks, including “the car attack in Quebec,” the attack on the War Memorial and Parliamentary building in Ottawa, “the hatchet assault in New York City,” and the car attack in Jerusalem.

He also cites the September 26 beheading in Oklahoma City.

Taking all these attacks into consideration — and the fact that ISIS encourages its Muslim adherents to engage in “lone wolf” attacks — Lott asks, “What can be done to protect public safety?” His answer: “When the police and military can’t be everywhere, the last line of defense is having more citizens carry guns.”