The Macedonians were of Greek descent. The Slavic tribes came to Macedonia hundreds to thousands of years later. They spoke Greek, they had Greek culture and they participated in the Olympic games. The Olympic games allowed only athletes of the Greek culture to participate.
But the Macedonian name as well as the culture and historical figures have been abused and stolen in an historical revisional attempt to create an own identidy for the Former Yugoslavian Republic Of Macedonia. There is a lot of propaganda going on the side of FYROM since they decided to have that create their national identity, that it let to grave and enduring disput with Greece.
Serious scholars of history all over the world almost alltogether side with Greece, so its a conflict that shouldnt really be there, if it were about historical facts.
Please check out this site:
http://macedonia-evidence.org/