What was the main reason for the split in the Indian National Congress at Surat in 1907?

The Surat Split of 1907 was primarily caused by the Extremists' lack of faith in the Moderates' methods of 'constitutional agitation' (petitions and prayers). The Extremists, led by Bal Gangadhar Tilak, Lala Lajpat Rai, and Bipin Chandra Pal, believed these methods were ineffective for achieving 'Swaraj' and doubted the Moderates' capacity to negotiate effectively with the British government following the 1905 Partition of Bengal.

This ideological divide deepened over the scope of the Swadeshi Movement. The Extremists wanted to extend the boycott nationwide and include all government institutions (schools, courts, and services), whereas the Moderates wanted to limit the movement to Bengal and avoid the use of passive resistance. The immediate trigger for the split was the disagreement over the presidency of the 1907 session: the Extremists proposed Lala Lajpat Rai or Tilak, while the Moderates insisted on Rash Behari Ghosh. The failure to reach a consensus on leadership and strategy led to the formal expulsion of the Extremists from the Congress.