Željava Air Base, situated on the border between Croatia and Bosnia and Herzegovina under Plješevica Mountain, near the city of Bihać, Bosnia, was the largest underground airport and military air base in the former Yugoslavia, and one of the largest in Europe. (Photo by Thomas Windisch/Exclusivepix Media)

An Afghan woman collects cotton buds at governmental farms in Jalalabad, Afghanistan, 20 October 2020. Afghanistan's agriculture and livestock department in Nangarhar province hire women and people in need of cash assistance to harvest cotton from their farms. (Photo by Ghulamullah Habibi/EPA/EFE)

General Maurice Gamelin, General Officer commanding the French Armies, is on a four day visit to England. He went to the staff college at Minley and is seen inspecting an anti-tank gun at Aldershot, on June 7, 1939. (Photo by AP Photo)

A young girl sits on a mat, as worshippers arrive to pray to mark the Muslim Eid-al-Adha (Festival of Sacrifices) without observationg precautionary measures to curb the spread of COVID-19, in Kara, Ogun State in southwest Nigeria, on July 31, 2020. Nigerian Muslim faithfuls joined their counterparts across the world to celebrate Eid-El-Adha, Islamic festival of sacrifice. (Photo by Pius Utomi Ekpei/AFP Photo)

An Afghan boy carries his wheelbarrow in Kabul, Afghanistan, Monday, August 5, 2019. (Photo by Rafiq Maqbool/AP Photo)

Fighters of the Popular Resistance Committees stand during a graduation ceremony of the affiliate special forces of the Popular Resistance, in Yemen's southwestern city of Taiz October 8, 2015. (Photo by Reuters/Stringer)

Soldiers stop to buy goods at the main market of Diffa, Niger, March 23, 2015. Diffa is where Nigerien and Chadian troops fighting insurgent group Boko Haram are based at. (Photo by Joe Penney/Reuters)

A member of the 324 Squadron during the Anzac Day dawn service at Coogee Beach in Sydney, Australia on 23 April 2019. Anzac Day, held annually on 25 April, is a national day of remembrance across Australia and New Zealand, which commemorates the people who lost their lives or served in wars and conflicts. The day coincides with the first landing of the Anzacs at Gallipoli, Turkey, in World War One. (Photo by Steven Saphore/Australian Associated Press)