Wikipedia
Delije is an umbrella name referring to the supporters of various sports clubs that compete under the Red Star Belgrade Sports Society banner. The name is derived from the Serbian word delija, meaning "brave, hero".
Though Red Star Sports Society has clubs in over twenty sports, Delije mostly focus on football ( FK Crvena zvezda) and basketball ( KK Crvena zvezda). The name Delije first began to be used by hardcore Red Star supporters during the late 1980s, with official inauguration taking place on 7 January 1989. Up to that point, the die-hard fans were scattered amongst about eight groups that shared the north stand at the Red Star Stadium (known colloquially as Marakana), most prominent of which were the Red Devils, Zulu Warriors and Ultras.
Delije organizational structure is fairly decentralized with many subgroups present at the stadium's north stand - the gathering point of the club's most loyal and passionate fans. At any given time, one or two subgroups assert themselves as the most prominent through dedication, regular attendance, willingness to fight, etc. and as a result get to hang their banners on the most visible parts of the stand, their leaders get to lead the chants, etc. Currently, the subgroup Belgrade Boys enjoys the greatest clout while others such as Ultra Boys, Brigate, Heroes and Ultras, also wield a lot of influence. In the past, subgroups such as Padina Corps, Kaluđerica and Fontana have all left their mark. Since Red Star enjoys a lot of support outside of Belgrade as well, various fan groups exist in cities across Serbia, Montenegro, and Republika Srpska. Those groups notably include Nišlije (from Niš), Kopre Nedri (from Republika Srpska), and several groups named after cities in Montenegro.
As a sign of appreciation, during the late 1990s, Red Star painted the word Delije in block letters across the north stand. Since the mid-1980s the supporters maintain friendly relations with Olympiacos CFP ultras - a friendship based on common Orthodox faith and same club colours. Since the mid-2000s FC Spartak Moscow fans are also included in this friendship.