An Israeli Merkava tank near the Hamas-controlled Gaza Strip border in southern Israel, on Thursday. The Pentagon confirms that Israel tapped a U.S. weapons stockpile for tank rounds. Debbie Hill/UPI/Landov hide caption

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A Minuteman III intercontinental ballistic missile can hit almost any target on earth ... but only if it flies through Russian airspace. This unarmed test version was launched from Vandenberg Air Force Base in California. V.A. Mouzon/Tech Sgt. Vincent Mouzon/U.S. Air Force hide caption

itoggle caption V.A. Mouzon/Tech Sgt. Vincent Mouzon/U.S. Air Force

First Lt. Patrick Romanofski (center) and 2nd Lt. Andrew Beckner (left) practice the launch of nuclear weapons. Promotions are now more strongly influenced by hands-on performance in this simulator. R.J. Oriez/U.S. Air Force hide caption

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In a photo taken on Thursday, smoke rises from a residential area in Tripoli, Libya. Deadly clashes erupted between Islamist fighters and pro-secular militias earlier this month. Hamza Turkia/Xinhua/Landov hide caption

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The city of Davenport, Iowa, is home to about 100,000 people. The city's mayor, Bill Gluba, wants the city to shelter some of the unaccompanied minors who have crossed the southern border of the U.S., but some members of the City Council oppose his efforts. scmcgee/Flickr hide caption

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Thousands of young immigrants, many of them from Central America, have crossed illegally into the United States this year, causing an unprecedented humanitarian crisis on the U.S.-Mexico border. John Moore/Getty Images hide caption

itoggle caption John Moore/Getty Images