The Rowlatt Act of March 1919 extended wartime emergency powers into peacetime, allowing detention without trial and trial without jury. Punjab, which had supplied half of India's soldiers in the war, took it as the reward for that.
Protests were general across the province. On 10 April two Congress leaders at Amritsar, Dr Saifuddin Kitchlew and Dr Satyapal, were deported from the city. A crowd going to petition the Deputy Commissioner was fired on. Rioting followed and several Europeans were killed.
On 13 April, Baisakhi, Brigadier General Reginald Dyer took fifty riflemen into Jallianwala Bagh, an enclosed ground with narrow exits, and ordered them to fire on a gathering of thousands without warning. Firing continued for about ten minutes, 1,650 rounds. The official count of the dead was 379. Other counts run past a thousand.
Martial law followed across five districts. Aircraft bombed a crowd at Gujranwala. Men were made to crawl on their bellies down a lane at Amritsar where an Englishwoman had been attacked. Public floggings were ordered.
The Hunter Committee censured Dyer and he was relieved. A subscription in Britain raised a large sum for him. Rabindranath Tagore returned his knighthood.
Punjab's participation in Indian nationalism after 1919 is not the same thing it was before.
The Act was recommended by a committee set up to examine wartime sedition, which had found the conspiracies largely finished. The legislation was passed anyway, and that is what made the reaction to it what it was.
The protests in Punjab were met with arrests, firing, martial law and the Jallianwala Bagh massacre on 13 April, in which several hundred people were killed in an enclosed ground.
The province had just supplied the largest share of the army in the war. What it received in return was the sequence that runs from the Act to the Bagh to the crawling order.