Officially formed in 1987—at the beginning of the first intifada—Hamas was built on a Muslim Brotherhood network that had existed in the Land of Israel since before 1948. Sean Durns presents a brief history of the group, arguing that it truly came into its own when it won the support of Tehran:
[In the 1970s], the Brotherhood began filling a void left by the Fatah-dominated PLO, which was busy carrying out terrorist attacks abroad from its home base in Lebanon and later from Tunis. . . . The year 1989, however, enshrined Hamas’s ascent. Beginning in January, Hamas and the Popular Front for the Liberation of Palestine (PFLP) sought to wrest control from the Unified National Leadership of the Uprising, which served as the principal organizing body during the intifada.
Perhaps most importantly, on November 16, 1989, Hamas announced that it had formed an alliance with the Islamic Republic of Iran. Relations between the two would wax and wane over the next three decades, but Tehran’s support has been crucial to Hamas’s power. Without Iranian largesse, it is unlikely that Hamas would have survived, much less grown to mount a full-scale challenge to Fatah, eventually seizing the Gaza Strip after besting the older movement in 2006 elections.