Milwaukee County Sheriff David Clarke has advised residents in a new PSA that they should consider taking a firearm safety course to defend themselves in a crisis as they wait for police to arrive. Gary Porter/AP/Milwaukee Journal-Sentinel hide caption

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President Obama shakes hands with his nominee to head the Defense Department, former Sen. Chuck Hagel, at the White House on Jan. 7. John Brennan, Obama's choice for director of the CIA, looks on. Alex Wong/Getty Images hide caption

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U.S. troops in Afghanistan appear to have mixed feelings about the decision lifting the ban on women in combat positions. Some women already operate in combat zones. Hospital Corpsman Shannon Crowley is shown here with her Marine Corps team in Musa Qala, Afghanistan, in November 2010. Paula Bronstein/Getty Images hide caption

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A female Israeli soldier runs during an urban warfare exercise at an army training facility near Zeelim, Israel, on June 19, 2008. Ed Ou/AP hide caption

itoggle caption Ed Ou/AP