Medic James E. Callahan of Pittsfield, Mass., gives mouth-to-mouth resuscitation to a dying soldier in war zone D, about 50 miles northeast of Saigon, June 17, 1967. Thirty-one men of the 1st Infantry Division were reported killed in the guerrilla ambush, with more than 100 wounded. (Photo by Henri Huet/AP Photo)

In this September 10, 1977, file photo, from left, Hua Guofeng, Chinese Communist Party (CCP) chairman and Mao Zedong's immediate successor; Ye Jianying, CCP vice chairman and future ceremonial head of state; Deng Xiaoping, no formal titles at the time but soon to emerge as paramount leader during the reform era; Li Xiannian, CCP vice chairman and future president; Wang Dongxing, head of the leadership bodyguard unit who helped topple the Gang of Four, view the body of later Chinese leader Mao Zedong in Beijing. (Photo via AP Photo)

A British Army Rolls Royce armoured car outside the Royal Ulster Constabulary police station on York Street in Belfast following riots after an Orange Order parade. (Photo by Fox Photos/Getty Images). 20th June 1935

Lightning strikes during a storm over the Ionian Sea in Calabria, Italy on June 27, 2016. (Photo by Alfonso Di Vincenzo/Pacific Press/Rex Features)

South Vietnamese-born designer Quasar drives the six-foot long square-shaped plastic car he built and which is scheduled to be a hit with the young driving set, in Paris, June 23, 1967. The car can be driven at speeds of up to 60 mph (Photo by Michel Laurent/AP Photo)

South Korean environmental activists wearing masks symbolizing the coronavirus attend a prevention campaign as South Koreans take measures to protect themselves against the spread of coronavirus (COVID-19) on March 30, 2020 in Seoul, South Korea. South Korea has called for expanded public participation in social distancing, as the country witnesses a wave of community spread and imported infections leading to a resurgence in new cases of COVID-19. According to the Korea Center for Disease Control and Prevention on Monday, 78 new cases were reported. The total number of infections in the nation tallies at 9,661. (Photo by Chung Sung-Jun/Getty Images)

Rachel Miner, 15, left, of Emmetsburg, Iowa, sits with Carlotta Haas, 15, a foreign exchange student from Duesseldorf, Germany, who had been living with Miner and her family but was called home, as they waited for her flight Wednesday, March 25, 2020, in at Minneapolis-St. Paul International Airport in Minneapolis. (Photo by Anthony Souffle/Star Tribune via AP Photo)

A young Sandinista guerrilla takes aim with his 45 pistol as he stands waiting to do combat with the Nicaraguan National Guard in Managua June 23, 1979. The guerrillas still occupy major parts of the Capitol City. (Photo by McLendon/AP Photo)