The Jallianwala Bagh massacre took place on 13 April 1919. Following the massacre, Sardar Udham Singh took revenge for it by shooting Michael O'Dwyer, the British officer who was the Governor General of Punjab. Sardar Udham Singh took revenge for the Jallianwala Bagh massacre by shooting Michael O'Dwyer, a British officer.

21 years after this massacre, on 13 March 1940, Sardar Udham Singh went to Caxton Hall in London and shot Michael O'Dwyer. Sardar Udham Singh had shot him while he was going to take his seat after delivering a speech at a meeting of the East India Association and the Royal Central Asian Society. Dyer died within minutes of being shot.