Anushilan Samiti
By 1902, Calcutta had three secret societies working toward the violent overthrow of British rule in India. One was founded by Calcutta student Satish Chandra Basu with the patronage of Calcutta barrister Pramatha Mitra, another was led by Bengali woman Sarala Devi and the third was founded by Aurobindo Ghosh. Ghosh was one of the strongest proponents of militant Indian nationalism at the time. By 1905 the work of Aurobindo and his brother, Barin, enabled Anushilan Samity to spread throughout Bengal. Nationalist writings and publications by Aurobindo and Barin, including "Bande Mataram" and "Jugantar", had a widespread influence on Bengal youth. The 1905 partition of Bengal stimulated radical nationalist sentiments in Bengal's Bhadralok community, helping Anushilan acquire a support base of educated, politically-conscious and disaffected members of local youth societies. Its program emphasized physical training, training its recruits with daggers and "lathis" (bamboo staffs used as weapons). The Dhaka branch of Anushilan was led by Pulin Behari Das, and branches spread throughout East Bengal and Assam. More than 500 branches were opened in eastern Bengal and Assam, linked by "close and detailed organization" to Pulin's headquarters at Dhaka. It absorbed smaller groups in the province, soon overshadowing its parent organisation in Calcutta. Branches of Dhaka Anushilan emerged in Jessore, Khulna, Faridpur, Rajnagar, Rajendrapur, Mohanpur, Barvali and Bakarganj. Estimates of Dhaka Anushilan Samiti's reach indicate a membership of 15,000 to 20,000. Within two years, Dhaka Anushilan devolved its aims from the Swadeshi to that of political terrorism.
Bagha Jatin
Several sources mention Jatin as being among the founders of the Anushilan Samiti in 1900, and as a pioneer in creating its branches in the districts. According to Daly's Report: "A secret meeting was held in Calcutta about the year 1900 [...] The meeting resolved to start secret societies with the object of assassinating officials and supporters of Government [...] One of the first to flourish was at Kushtea, in the Nadia district. This was organised by one Jotindra Nath Mukherjee ["sic"!].". Nixon reports further : "The earliest known attempts in Bengal to promote societies for political or semi-political ends are associated with the names of the late P. Mitter, Barrister-at-Law, Miss Saralabala Ghosal and a Japanese named Okakura. These activities commenced in Calcutta somewhere about the year 1900, and are said to have spread to many of the districts of Bengal and to have flourished particularly at Kushtia, where Jatindra Nath Mukharji ["sic"!] was leader." Bhavabhushan Mitra's written notes precise his presence along with Jatindra Nath during the first meeting. A branch of this organisation (Anushilan Samiti), was to be inaugurated in Dacca. In 1903, on meeting Sri Aurobindo at Yogendra Vidyabhushan's place, Jatin decides to collaborate with him and is said to have added to his programme the clause of winning over the Indian soldiers of the British regiments in favour of an insurrection. W. Sealy in his report on "Connections with Bihar and Orissa" notes that Jatin Mukherjee "a close confederate of Nani Gopal Sen Gupta of the Howrah Gang (...) worked directly under the orders of Aurobindo Ghosh."