An Israeli 155mm self-propelled howitzer, loaded on a trailer, arrives at a position along the Israel-Gaza border on May 13, 2021. Israel deployed additional troops to Gaza's border as the military conflict with Palestinian Islamists raged on, while inside Israel security forces scrambled to contain deadly riots between Jews and Arabs. (Photo by Emmanuel Dunand/AFP Photo)

North Korean children wave to people on a Chinese tourist boat on the banks of Yalu River near the Chongsong county of North Korea, opposite the Chinese border city of Dandong, May 8, 2011. (Photo by Jacky Chen/Reuters)

A woman and a child make a bonfire at a makeshift camp for migrants and refugees at the Greek-Macedonian border near the village of Idomeni, Greece, April 1, 2016. (Photo by Marko Djurica/Reuters)

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)

Border Security Force (BSF) soldiers ride their camels as they take part in a rehearsal for a road show ahead of the visit of U.S. President Donald Trump, in Ahmedabad, India, February 21, 2020. (Photo by Amit Dave/Reuters)

A girl attends a performance hosted by the Ministry of the Interior that includes police, border guards, and rescuers celebrating International Children's Day in Kyiv, Ukraine on June 1, 2021. (Photo by Gleb Garanich/Reuters)

North Korean soldiers wave along the Yalu River, near the North Korean town of Sinuiju, opposite to the Chinese border city of Dandong October 7, 2014. (Photo by Jacky Chen/Reuters)

Children play at a makeshift camp for migrants and refugees at the Greek-Macedonian border near the village of Idomeni, Greece, March 29, 2016. (Photo by Marko Djurica/Reuters)