It was during O'Dwyer's tenure as Punjab's Lieutenant Governor that the Jallianwala Bagh massacre occurred in Amritsar, on 13 April 1919. As a result, his actions are considered one of the most significant factors in the rise of the Indian independence movement. O'Dwyer endorsed Reginald Dyer's action at Jallianwala Bagh, making it clear that he felt Dyer's orders to shoot at the crowds was correct. He subsequently administered martial law in Punjab, on 15 April, and backdated it to 30 March 1919.