Reginald Dyer in the context of "Jallianwala Bagh massacre"

The Jallianwala Bagh massacre (IPA: [dʒəlɪjãːʋaːlaː baːɣ, baːɡ]), also known as the Amritsar massacre, took place on 13 April 1919. A large crowd had gathered at the Jallianwala Bagh in Amritsar, Punjab, British India, during the annual Baisakhi fair to protest against the Rowlatt Act and the arrest of pro-Indian independence activists Saifuddin Kitchlew and Satyapal. In response to the public gathering, Brigadier-General Reginald Dyer surrounded the people with Gurkha and Sikh infantrymen of the Indian Army. The Jallianwala Bagh could only be exited on one side, as its other three sides were enclosed by buildings. After blocking the exit with his troops, Dyer ordered them to shoot at the crowd, continuing to fire even as the protestors tried to flee. The troops kept on firing until their ammunition was low and they were ordered to stop. Estimates of those killed vary from 379 to 1,500 or more people; over 1,200 others were injured, of whom 192 sustained serious injury. Britain has never formally apologised for the massacre but expressed "deep regret" in 2019.

The massacre caused a re-evaluation by the Imperial British military of its role when confronted with civilians to use "minimal force whenever possible" (although the British Army was not directly involved in the massacre; the Indian Army was a separate organisation). However, in the light of later British military actions during the Mau Mau rebellion in the Kenya Colony, historian Huw Bennett has pointed out that this new policy was not always followed. The army was retrained with less violent tactics for crowd control.