In this aerial view the officers' building and an auditorium stand at the former Soviet military base on January 26, 2017 in Wuensdorf, Germany. Wuensdorf, once called “The Forbidden City”, was the biggest base for the Soviet armed forces in communist East Germany from 1945 until the last Soviet troops left in the early 1990s following the end of the Cold War and the reunification of Germany. (Photo by Sean Gallup/Getty Images)

In this November 2, 2017 photo, Mathew Fulkerson and his wife Leigh Ann pose at their Subterra Airbnb located in a former underground missile silo base near Eskridge, Kan. It was designed to house a nuclear warhead six decades ago – but now, this Cold War silo is the perfect spot for a mini break at just $133 a night. (Photo by Thad Allton/The Topeka Capital-Journal via AP Photo)

A policewoman wipes her tears as she stands in front of metal caskets containing the bodies of Special Action Force (SAF) police who were killed in Sunday's clash with Muslim rebels, at Villamor Air Base in Pasay city, metro Manila January 29, 2015. Philippine President Benigno Aquino urged legislators on Wednesday not to abandon a plan for autonomy for Muslims to end a decades-old insurgency after the clash in which dozens of people were killed, saying doing so would dash hopes for peace. (Photo by Romeo Ranoco/Reuters)

Maj. Matt O'Donnell of Glenelg, MD shields himself from rotor wash as Ospreys carrying the delegation of U.S. Secretary of Defense Leon Panetta leaves on March 14, 2012 at Forward Operating Base Shukvani, Afghanistan. Panetta is also scheduled to meet with President Karzai during his two-day visit to Afghanistan. The trip comes as the Taliban has vowed revenge following this past weekend's killing spree by a U.S. soldier who is accused of killing 16 civilians in Afghanistan. Most of those killed were children and women. (Photo by Scott Olson/Getty Images)

RAF Tornados fly above the Lossiemouth air base on March 18, 2011 in Lossiemouth, Scotland. UK defence forces will help to enforce a no-fly zone over Libya after the UN voted in favour of a resolution that backed 'all necessary measures', except a foreign occupation force, to protect Libyan civilians.

A military AWAC aircraft lands at the British RAF Akrotiri airbase on March 20, 2011 in Cyprus. Defence analysts said the sovereign military airfield at Akrotiri could be used by the RAF to help enforce a no-fly zone over Libya against Col Gaddafi’s offensive against outgunned Libyan rebels. (Photo by Matt Cardy/Getty Images)

Golden monkeys play at a conservation base in Shennongjia, central China's Hubei Province, January 26, 2018. The golden monkey conservation base witnessed a snowfall recently. (Photo by Du Huaju/Xinhua/Barcroft Images)

Somali security officers gather at the scene of a car bomb attack at the base for the African Union forces in Mogadishu, Somalia, 26 July 2016. Media reports say at least 10 people, including the security guards at the base which is located at Mogadishu's airport, have been killed after two car bombs exploded at the base. Somalia's Islamist militant group al-Shabab has claimed responsibility for the latest attack. (Photo by Said Yusuf Warsame/EPA)