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US President Barack Obama (R) and Japanese Prime Minister Shinzo Abe shake hands after laying wreaths at the Hiroshima Peace Memorial Park in Hiroshima on May 27, 2016. (JIM WATSON/AFP/Getty Images)

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People hold the Polish constitution as they attend the anti-government demonstration against the refusal of polish government to accept verdict of Constitutional Court in Warsaw, March 10, 2016. (WOJTEK RADWANSKI/AFP/Getty Images)

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Sinking hit British battlecruiser 'Indefatigable' shortly before its explosion on May 31st, 1916 - tempera painting by Willy St?wer 1916. (Willy St?wer/ullstein bild via Getty Images)

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Members of the 3rd U.S. Infantry Regiment place American flags at the graves of U.S. soldiers buried in Section 60 at Arlington National Cemetery in preparation for Memorial Day May 24, 2012 in Arlington, Virginia. (Win McNamee/Getty Images)