Trotsky defended his position in a series of seven letters which were collected as "The New Course" in January 1924. The illusion of a "monolithic Bolshevik leadership" was thus shattered and a lively intra-Party discussion ensued, both in local Party organizations and in the pages of "Pravda". The discussion lasted most of December and January until the XIIIth Party Conference of 16–18 January 1924. Those who opposed the Central Committee's position in the debate were thereafter referred to as members of the Left Opposition.