Mahatma Gandhi returned to India from South Africa in 1915. In South Africa, he had successfully fought the racist regime with a notel method known as Satyagraha.
The three reasons stating the fact are
(i) The idea of Satyagraha emphasised the power of truth which would ultimately triumph; Gandhiji believed that the dharma of non-violence could unite all Indians.
In India, Gandhiji launched Satyagraha movements in various areas like Champaran, Kheda and Ahmedabad.
(ii) In 1919, the Rowlatt Act was passed by the Imperial Legislative Assembly which gave enormous power to the British Government.
The government could detain any political prisoner without any trial for two years. The aim of this Act was to repress political activities of the nationalists. People were agitating against the law.
(iii) On 13th April, 1919, the infamous incident took place where hundreds of innocent people were killed. As the news of Jallianwalla Bagh spread, widespread movement started.
Gandhiji now felt the need to launch a more broad based movement in India.