What is Hamas? The group that rules the Gaza Strip has fought several rounds of war with Israel

In this Dec. 14, 2014, file photo, masked Palestinian gunmen of the Hamas militant group hold weapons during a rally to commemorate the 27th anniversary of the group in Gaza City. (AP Photo/Khalil Hamra, File)

Hamas, which has ruled the Gaza Strip since 2007, launched an attack inside Israel over the weekend, killing hundreds and taking others hostage. Its unprecedented breach of the border sent fighters inside border communities and military installations, shocked Israel and its allies and raised questions about the group’s capabilities and strategy.

What is Hamas?

The group was founded in 1987 by Sheikh Ahmed Yassin, a Palestinian refugee living in Gaza, during the first intifada, or uprising, which was marked by widespread protests against Israel’s occupation.