Martial law was imposed on five Punjab districts after 13 April 1919 and lasted about two months. What happened under it is less known than Jallianwala Bagh and was in aggregate more extensive.
At Amritsar, Indians passing along the lane where an Englishwoman had been attacked were made to crawl on their bellies. Public floggings were carried out at fixed posts. Students were made to walk sixteen miles a day for roll calls.
At Gujranwala on 14 April, aircraft bombed and machine-gunned a crowd and the town, which is one of the earliest uses of aerial attack against a civilian population anywhere.
Summary tribunals passed death sentences at Lahore and elsewhere, later commuted. Whole villages were fined collectively.
The Hunter Committee documented much of this in 1920 and the Congress Punjab Inquiry Committee documented more.
Jallianwala Bagh is remembered as a single atrocity. It was the opening of a two-month administrative operation across a province, and that is the part that changed Punjab's politics.
Martial law was declared across several Punjab districts after the disturbances of April 1919 and was administered by summary tribunals with wide powers.
The crawling order at Amritsar required Indians to move on their hands and knees along a lane where a British woman had been assaulted. Public floggings were carried out in several towns.
An aeroplane bombed a crowd at Gujranwala. The Hunter Committee that inquired afterward divided along racial lines and its minority report is the sharper document.