May 17th, 1980 – In an effort to suppress student demonstrations, General Chun Doo-hwan of South Korea seizes control of the government and declares martial law.
May 19th, 1959 – North Vietnam forms Group 559 to build the Ho Chi Minh Trail to maintain supply lines to South Vietnam.
May 20th, 1969 – Vietnam War: The Battle of Hamburger Hill in Vietnam ends.
May 22nd, 2012 – The 634 meter tall Tokyo Skytree opens to the public. It is the world's tallest freestanding broadcasting tower.