Bahrain is a small island country in the Persian Gulf, just off the coast of Saudi Arabia. It’s only about 780 square kilometers in area, into which are packed about a million and a half people. Like the other Gulf states, it’s an absolute monarchy under the Khalifa dynasty and only about half the population are citizens, with the rest being foreign workers. Unlike the other Gulf states, though, the majority of the citizen population are Shia Muslims, while the Khalifa dynasty is Sunni.
Bahrain’s Shia are generally discriminated against, shut out from any positions of power and living in poverty. During the Arab Spring, Bahrain experienced massive but peaceful protests against the monarchy, mostly by its Shia majority. Saudi Arabia feared the possibility of a Shia-dominated state just off its coast and sent in military forces, massacring protesters and crushing the uprising.
There have been a few efforts to get protests started again, and a half-hearted Shia insurgency that never accomplished much, but the regime and its Saudi guarantors were too strong and ruthless to overcome.