Hamas has been a contentious rival to Fatah since Hamas was founded in 1988. Fatah has tried to garner support on the international stage by implicitly accepting Israel and pushing toward a Palestinian state. But those policies have lessened its stature among Palestinians, some of whom instead turned toward Hamas and its absolute rejection of a two-state solution.
The two groups have alternately cooperated against Israel and violently clashed with each other over the years. They also competed in the political arena in 2006, when Hamas entered legislative elections for the first time and topped Fatah, winning a majority of seats in the Palestinian Authority. International donors, which provide much of the Palestinian Authority's budget, cut off aid when Hamas refused to recognize Israel's right to exist.
In December of that year, the rivalry turned violent again as sporadic battles broke out between the two factions' security forces. In June 2007, Hamas gunmen drove Fatah's forces out of Gaza. Fatah's security returned the favor days later, expelling Hamas from the West Bank. The two groups remained at odds until May 2011, when they signed a reconciliation agreement to mend the split and strengthen Palestinians' bid for statehood.