The Defence of India Act 1915, also referred to as the Defence of India Regulations Act, was an emergency criminal law enacted by the Governor-General of India in 1915 with the intention of curtailing the nationalist and revolutionary activities during and in the aftermath of the First World War.⁣

Unlike the English law ‘Defence of the Realm Acts’ which was limited to persons of hostile associations or origin, the Defence of India act could be applied to any subject of the King and was used to an overwhelming extent against Indians.⁣

The act was first applied during the First Lahore Conspiracy trial in the aftermath of the failed Ghadar Conspiracy of 1915, and was instrumental in crushing the Ghadar movement in Punjab and the Anushilan Samiti in Bengal.⁣

The enactment of the law saw 46 executions and 64 life sentences handed out to revolutionaries in Bengal and Punjab in the Lahore Conspiracy Trial and Benares Conspiracy Trial, and in tribunals in Bengal. By March 1916 widespread arrests helped Bengal Police crush the Dhaka Anushilan Samiti in Calcutta.⁣

It was not limited to those suspected of revolutionary crimes. It gradually came to be used in suppressing the voice of many nationalist leaders, even of moderate views. ⁣

A number of prominent moderate leaders were interned or deported under the this act. Most notable of these leaders was Mrs Annie Besant for Home Rule movement. Abul Kalam Azad was also deported from Bengal and placed under house arrest in Ranchi for his writing in Al Balagh under this act.⁣

By 1918 there were about 800 internees detained under this and other provisions. The act, being a wartime measure, was due to expire six months after the end of hostilities. The extension of its provisions in the Rowlatt Acts of February 1919 started the agitation that led to the noncooperation movement of Mahatma Gandhi in 1920–22.⁣

The act was re-enacted during World War II as Defence of India act 1939. ⁣

Independent India retained the law in a number of amended forms, which have seen use in proclaimed states of national emergency including Sino-Indian war, Bangladesh crisis and The Emergency of 1975 etc.