Reuters historical calendar - August 20

London, Aug 19 (Reuters) Following are some of the major events to have occurred on August 20 since 1900: 1914 - The German army captured Brussels as the Belgian army retreated to Antwerp.

1940 - Leon Trotsky, Russian revolutionary, was fatally wounded by a Spanish Communist with an ice pick in Mexico City, dying the next day. The Soviet government denied responsibility.

1949 - A new assembly in Hungary adopted a Soviet-style constitution and renamed the country the Hungarian People's Republic.

1953 - French forces deposed the Sultan of Morocco, Sidi Mohammed ben Youssef.

1960 - Senegal decided to withdraw from the Mali Federation which it had formed with French Soudan (now Mali) in 1959.

1961 - East Germany began to erect a 5 foot - high wall along the border between East and West Berlin to replace the barbed wire put up on August 13.

1968 - Soviet and Warsaw Pact troops crossed the border into Czechoslovakia just before midnight, at the start of an invasion to crush the ''Prague Spring'' reforms.

1971 - The first electronic pocket calculator was introduced. Made by Texas Instruments, it was battery powered and weighed 2.5 pounds.

1977 - The American Voyager II spacecraft was launched on its mission to explore the outer planets. It passed close to Jupiter (July 1979), Saturn (August 1981), Uranus (January 1986) and Neptune (August 1989) before leaving the solar system.

1978 - Palestinian guerrillas attacked an El Al airline bus in London, killing two people.

1980 - The Italian climber Reinhold Messner made the first successful solo ascent of Mount Everest.

1988 - The UN-brokered ceasefire in the Iran-Iraq war, announced on August 8, came into effect.

1991 - Parliament in the Baltic republic of Estonia declared immediate full independence from the Soviet Union.

1995 - At least 350 people were killed in India's worst train disaster when two Delhi-bound trains collided at Firozabad, 200 km from the Indian capital.

1995 - Liberia's main warring factions signed a peace accord calling for a ceasefire to end more than five years of civil war and to start democratic rule within one year.

1998 - The United States launched cruise missile strikes against bases in Afghanistan and a factory in Sudan, saying they were linked to the bombings of US embassies in Kenya and Tanzania.

2003 - Libya began transferring 2.7 billion dollars to the Bank for International Settlements to compensate families of the victims of the 1988 airliner bombing over Lockerbie, Scotland.

2003 - Argentina's Senate annulled amnesties for military officers who tortured and murdered leftists during the 1976-1983 ''Dirty War''.

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