20 APRIL

1572 - "Relation of the Conquest of the Island of Luzon," which narrates the conquest of the island of Luzon, is published in Manila in the new Spanish colony of the Philippine Islands; authored anonymously, it  describes how the colonizing Spanish forces captured Manila from the Moros, discussing the campaigns that led to the subjugation of the island -- from the experiences of the Spaniards in Panay to their eventual exploration and pacification of Luzon.

1953 - The United Nations and Korea begin exchanging sick and wounded prisoners of the Korean War at Panmunjon, a mile away from the north-south border where fighting continues: 100 UN prisoners and 400 North Koreans and 100 Chinese are freed; the Korean War staged between joint Nokor and Chinese forces and US-led UN forces will end in July with the signing of armistice restoring the 38th parallel between North and South Korea.

1968 - Mount Mayon in the Philippines, an active stratovolcano with a 'perfect cone', explodes and sends 3,000-foot-high fire balls, along with lave and steam, hurtling out; around 70,000 people comprising the population within the 6-mile diameter danger zone area of the volcano located in Albay province in the Bicol region escape unscathed because the government has earlier evacuated them to safer grounds.

1971 - The United States Supreme Court unanimously upholds the use of busing to achieve racial desegregation in schools in the bid "to dismantle the dual school systems of the South"; civil rights organizations had been dismayed by the Nixon Administration's intervention for the side of Southern school systems who wanted to be allowed to assign students to schools in their own neighborhoods even if this resulted in slowing the pace of desegregation in the South.