What was the primary reason for the split between the Bolsheviks and Mensheviks in 1903?

The split between the Bolsheviks and Mensheviks in 1903 primarily stemmed from fundamental ideological differences regarding party organization and leadership rather than personal animosities. The Bolsheviks, led by Lenin, favored a tightly organized party of professional revolutionaries who would lead the proletariat in revolution. In contrast, the Mensheviks advocated for a broader, more democratic structure that would include a wider array of membership and input from the working class.

This divergence in how the party should be structured and how effectively it should guide the working class towards revolution was not just a matter of personality but reflected deeper philosophical divides about how to achieve social change and what the role of the party should be in that process. The split thus crystallized these strategic differences, leading to the formation of two distinct factions within the Russian socialist movement. This foundational divide ultimately influenced their approaches to the revolution and the subsequent shaping of the Soviet state.