New Delhi: It took 21 years, travel across three continents and several countries for Shaheed Udham Singh to avenge the death of hundreds of innocent Indians killed by General Michael O'Dwyer -- the butcher of Jallianwala Bagh in Amritsar on 13 April 1919.

During the struggle for independence, Dwyer was responsible for the massacre of hundreds of unarmed Indians inside the Jallianwala Bagh, after which Udham Singh decided that he would avenge the death of his fellow Indians by killing him.

Singh travelled to Africa, South America and Europe extensively to get an opportunity to kill Dwyer and reached London in 1934 to track down his target. He started living on the Alder Street Commercial Road in London and waited for the right time to carry out his mission.

To achieve the only aim left in his life, Singh bought a revolver with six bullets and looked for the right time and place to kill Dwyer. He came to know that Dwyer would be attending a meeting at the Royal Central Asian Society on 13 March 1940.

Singh prepared a meticulous plan for the last leg of his action. He bought a thick book that could hide his weapon and cut its pages inside in the shape of a revolver.

As soon as Dwyer reached the meeting with his friends, Singh took a position behind a wall and started firing at him. Two of his bullets killed Dwyer right on the spot while two of the companions of Dwyer suffered injuries.

Singh did not run away from the spot. He waited for the police to arrest him. He was arrested and, later, tried by a court in London.

During his trial, Singh said he had killed Dwyer because the general deserved to die as the condition of Indians under the British rule was very poor and it was his duty as an Indian to take the action for the country.

After a one-sided trial, on 4 June 1940, Udham Singh was held guilty for the killing of Dwyer and given the capital punishment on 31 July 1940 in a jail in London.