The Civil Disobedience Movement, launched in March 1930, unleashed an unprecedented wave of mass participation in the country. In the region in and around Gomia town of present-day Bokaro district of Jharkhand, the Santhals joined the movement under the leadership of Bangam Manjhi.
A native of Borobera village, Bangam Manjhi had emerged as a spiritual and political leader of the Santhals as he led the community in a reform movement called the 'Sacred Thread Movement'. Manjhi advised Santhals to don the red sacred thread and abstain from non-vegetarian food. Manjhi himself claimed to be a disciple of Mahatma Gandhi and promoted several of his ideas, such as the exclusive use of khadi.
As the Santhal movement spread along with the Civil Disobedience Movement, many Santhals stopped paying the Chaukidari tax. The Santhals received the support of local Congress leaders such as Krishna Ballav Sahay and Ram Narayan Singh, whose arrests generated much steam and gave thrust to Santhal participation in the national movement. Santhals held secret meetings on every full moon, and on 31 May 1930, around 210 Santhals adopted the sacred thread.
The burgeoning Santhal movement made the British administration extremely uneasy, for the British suspected it as the seeds of another Santhal uprising. The British made several arrests. On 4 July 1930, Bangam Manjhi was arrested and put into jail after which the Santhal movement faced a decline.
Source: Indian Culture Portal