U.S. Army helicopters providing support for U.S. ground troops fly into a staging area fifty miles northeast of Saigon, Vietnam, August 28, 1966. Helicopter fuel is stored in the large rubber tanks, foreground. (Photo by Henri Huet/AP Photo)

A riot policeman fires into the air during clashes with opposition supporters at a rally demanding a referendum to remove President Nicolas Maduro in Caracas, Venezuela, May 11, 2016. (Photo by Carlos Garcia Rawlins/Reuters)

In this Sunday, May 29, 2016 photo, fighters take a selfie while firing artillery during fight against Islamic State militants in Fallujah, Iraq. Iraqi forces this week pushed into the city's southern sections after securing surrounding towns and villages more than 50,000 people are believed to be trapped inside the Sunni majority city, about 65 kilometers (40 miles) west of Baghdad. (Photo by Anmar Khalil/AP Photo)

Dressed up as Punxsutawney Phil, Marty Nagy, of Hallandale Beach, Fla., gives thumbs up to passers by before the start of the 12th annual Groundhog Day on Hollywood Beach, Tuesday, February 2, 2016, in Hollywood, Fla. The event, which featured breakfast and an ocean plunge, benefited the Hollywood Beach Lifeguard Competition Team. (Photo by Wilfredo Lee/AP Photo)

Boys play with a drainage culvert used for flood control in Las Pinas, Metro Manila February 28, 2016. (Photo by Erik De Castro/Reuters)

Visitors dressed in superhero costumes attend the Paris Comics Expo at the Parc Floral in Paris, France, April 15, 2016. (Photo by Charles Platiau/Reuters)

Sumo wrestlers compete during the annual “Honozumo” ceremonial sumo tournament dedicated to the Yasukuni Shrine in Tokyo, Japan, April 18, 2016. (Photo by Yuya Shino/Reuters)