In 1962, China launched an attack on India on October 20, in what famously came to be known as Indo- China war or Sino- Indian war of 1962. The fight was between 10,000-20,000 Indian troops and 80,000 Chinese troops. The war continued for about a month and ended on 21st November 1962 after China declared ceasefire.
The National Solidarity Day is observed every year in India in remembrance of this day, when India was attacked by China 56 years ago.