In April 1913, Indians in Astoria, Oregon, formed Hindustani Association of the Pacific Coast with its main objective to liberate India from the British colonialism and help establish a free and independent India. The headquarter of the association was established in San Francisco and a newspaper titled Gadar was launched for free distribution to promote the aims, objectives and activities of the association. Gadar was published in Punjabi and Urdu and in some other Indian languages and was sent to Indians all over the world. Kartar Singh was put in charge of Gadar in Punjabi language. It carried articles about the atrocities of the British on Indians and racial prejudice and discrimination against Indians in the United States. The articles exhorted people to join the association, and urged them to unite and rise up against the British rule. The Gadar magazine became very popular for its revolutionary and patriotic ideas and over a period of time, the Hindustani Association of the Pacific Coast itself became known as the Gadar Party. 

The organization was still very young, when in August, 1914, World War I broke out, and the British forces got busy fighting war against the Germans. The Gadarites decided that the time for action had come as World War I provided them a golden opportunity to attain their goal. They published ‘declaration of war’ against the British in the August issue of Gadar and sent to Indians everywhere, especially to Indian soldiers in British cantonments. The Gadarites inspired thousands of Indians who left for India for rebellion and to overthrow the British Government. 

Kartar Singh left the United States on September 15, 1914, with Satyen Sen and Vishnu Ganesh Pingle. They met with the well-known revolutionary Rash Behari Bose in Benares and shared their plans for throwing the British out of India. Unfortunately, this information reached the British and several Gadarites were arrested at the ports on landing. Meanwhile, Kartar Singh went about preparing the base for the revolution in Punjab. He drew plans to infiltrate the Indian army, went to several cantonments with Pingle to excite the soldiers to fight – not for the British but against the British Empire – and free India from the shackles of British imperialism.