The Komagata Maru incident involved the Japanese steamship Komagata Maru, on which a group of people from British India attempted to immigrate to Canada in 1914, but most were denied entry and forced to return to Calcutta, India.
The individual who hired the Komagata Maru and who acted as chief spokesperson for the passengers was a wealthy Sikh named Gurdit Singh Sirhali who was then in his mid-50s. He had made his money as an importer and contractor in Malaya and Singapore.
The ship sailed from Hong Kong on 4 April 1914 with just 150 passengers. As the ship proceeded via Shanghai and the Japanese ports, number reached 376 consisted of 337 Sikhs, 27 Muslims, and 12 Hindus.
In 1908, Canadian government passed an order by which canadian immigration officers were empowered to block the entry of anyone who came to Canada other than by a continuous journey from their home country and any Asians who arrived with less than $200, a very large sum of money in 1914. (This did not apply to Chinese and Japanese, who were kept out by other measures).
These two regulations were deliberately deceptive because, while they were designed solely to exclude immigrants from India,
These passengers arrived in Canadian waters on 21 May 1914 and anchored in Vancouver’s harbor on 23 May. None of the passengers was allowed ashore, even for preliminary examination, except for 20 returning residents and a very few special cases.
Komagata stayed there for about two months and soon ration started running low. British Columbia Court gave decision in government favour. Gurdit Singh and the passengers accepted the decision of the British Columbia Court of Appeal without attempting an appeal to the Supreme Court of Canada.
Finally, on 23 July, 355 disappointed and radicalized passengers left for Asia. After a long delay in Japan, where some passengers disembarked, 321 passengers reached the Indian port of Budge Budge near Kolkata on 29 September 1914.
There, the Indian Imperial Police attempted to arrest the group leaders. A riot ensued, and they were fired upon by the police, resulting in the deaths of 20 Sikhs.
You might wonder if Canadian government has put strict regulation on upcoming immigrant in 1908 then why did Gurdit Singh decided to sail in 1914?
That is because in November 1913 Canadian judge overruled an immigration department order for the deportation of 38 Punjabi Sikhs. These immigrants had come to Canada via Japan on a regularly scheduled Japanese passenger liner, the Panama Maru. Which encouraged the sailing of the Komagata Maru in the following April 1914.
Unfortunately, by April the legal situation had changed. The Canadian government had quickly rewritten its regulations to meet the objections it encountered in court by January 1914, three months before the Komagata Maru left Hong Kong for Vancouver.