I assume with ‘Macedonians’ you mean Slavic Macedonians living in the Former Yugoslav Republic of Macedonia (FYROM), who are distinct from the Greek Macedonians that live in the Greek province of Macedonia. This distinction lies at the heart of the naming conflict between the FYROM and Greece I wrote a paper about a year ago. The separation of Slavic Macedonians from the Bulgarians in terms of history is a quite ‘recent’ phenomenon and like most elements of Slavic Macedonian history a modern construct. For most of its history Slavic-Macedonian history was very much related with the history of the Serbs, Bulgarians and Greeks.
The language spoken by the Slavic Macedonians, Macedonian, is closely related to Bulgarian. Indeed, the Bulgarian reading of history claims that the language of the people of the Republic of Macedonia is merely a dialect of Bulgarian. As an extension of this attitude the Bulgarians believe that the people and the territory of the Republic of Macedonia belong, both historically and culturally, to the Bulgarian nation. Because of this the Bulgarians effectively deny the existence of a distinctive Slav-Macedonian nation. The creation of the Bulgarian Exarchate in the late 19th century, a separation of the Bulgarians from the Greek Orthodox Church was what instigated the division of Macedonia amongst the Bulgarians, Greeks and Serbians. The Bulgarians state attempted to regain what it regarded as lost Macedonian territory from Serbia and Greece by aligning itself with Germany during both World Wars.
It was the end of the Second World War and the founding of the Socialist Yugoslavian Republic that allowed the Slavic Macedonians to consolidate a national identity distinct from the Serbs, Greeks and Bulgarians. This effort was encouraged by the central Yugoslav government in Belgrade, which sought to dispel any Greek and Bulgarian claims on the territory. Examples of this realization of identity were the founding of the Macedonian Orthodox Church and the codification of the Macedonian language. These elements provided instruments for the Slavic Macedonians with which they could set themselves apart from their neighbours and reject any claim form Serbian, Greek or Bulgarian side that they were merely an offshoot of their respective nations and therefore not deserving of their own identity.
The construction of such a new identity, separated from already established ones, saw the new Slavic Macedonian nation morphing cultural elements shared with the Bulgarians or the Greeks to fit their newly created nation’s history. The codification of ‘the separate Macedonian language’ was very unappealing to the Bulgarians, as it rejected their claim that the Slavic Macedonians belonged to their nation and were in fact speaking a dialect of their language. The Slavic Macedonians took possession of this ‘dialect’ and used it as a basis for their newly created identity.The question of Slavic-Macedonian identity is determined by the view the Bulgarians, Greeks and Slavs of Macedonia have regarding Slavic-Macedonian national identity.
Sources:
Triandafyllidou, A., Calloni, M. & Mikrakis, A. (1997). New Greek Nationalism. Sociological Research Online. 2 (1)
Engstrom, J. (2002). The power of Perception: The Impact of the Macedonian Question on Inter-ethnic Relations in the Republic of Macedonia. The Global Review of Ethnopolitics. 1 (3). Pp. 3-17
This is my first submission here, I hope my answer clears up some of the questions you had.