1520: Battle of Otumba, Mexico: Hernán Cortés and the Tlaxcalans defeat a numerically superior Aztec force

1937: Japanese and Chinese troops clash at the Marco Polo Bridge, beginning the Second Sino-Japanese War

1947: Alleged and disputed Roswell UFO incident

2005: Coordinated terrorist bomb blasts strike London’s public transport system during the morning rush hour killing 52 and injuring 700

2005: Influenced by global Live 8 concerts, G8 leaders pledge to double 2004 levels of aid to Africa from US$25 to US$50 billion by the year 2010

Source: Onthisday.com