Ukrainian state emblem is seen on a gun's holster as soldiers guard naval base in the village of Novoozernoye, some 91 km west of Crimean capital Simferopol, Ukraine, on Monday, March 3, 2014. Ukraine says Russian forces controlling the strategic region of Crimea are demanding that the crew of two Ukrainian warships in Sevastopol's harbor must surrender. (Photo by Ivan Sekretarev/AP Photo)

German field telegraph operators at work in Warsaw. (Photo by Hulton Archive/Getty Images). 1st October 1914

An Indonesian muslim woman walks on “sea of sands” as they prepare for Eid Al-Fitr prayer at Parangkusumo beach on July 17, 2015 in Yogyakarta, Indonesia. Muslims worldwide observe the Eid Al-Fitr prayer to mark the end of Ramadan and the beginning of the new month of blessing Shawwal 1436 Hijriah. (Photo by Ulet Ifansasti/Getty Images)

Lowry Park Zoo elephants Matjeka, 23, and her 1-year-old daughter, Mavi, apply a liberal coating of “sunscreen” to themselves in a clay mud wallow at the park Tuesday, August 12, 2014, in Tampa, Fla., on the park's first observation of World Elephant Day to raise awareness of the wild African elephant crisis. “Elephants are prone to being sunburned”, said associate curator Chris Massaro. “What they need is lot of mud or clay to roll around in and cover up their skin so it will protect it from the sun”. (Photo by Cherie Diez/AP Photo/The Tampa Bay Times)

Somali men carry swordfish from the sea to a market in the capital Mogadishu, Somalia Thursday, April 23, 2015. (Photo by Farah Abdi Warsameh/AP Photo)

A rebel fighter celebrates as his comrades fire a rocket barrage toward the positions of troops loyal to Libyan ruler Muammar Gaddafi April 14, 2011 west of Ajdabiyah, Libya. Rebels exchanged artillery and rocket fire with loyalist troops west of Ajdabiyah April 14 as the confict engulfing Libya continued. (Photo by Chris Hondros/Getty Images)

A People's Liberation Army (PLA) commando jumps through a fire hoop part of an exercise during an open day event at the Ngong Shuen Chau Barracks, the PLA navy base in the territory, in Hong Kong, China, 01 July 2015. Thousands of visitors attended the PLA open day yesterday and today to mark the 16th anniversary of the handover from British rule. (Photo by Jerome Favre/EPA)