Who are Hamas?
Hamas is an acronym of the group's name which means "Islamic Resistance Movement". They are a Palestinian Sunni Islamic organisation with an associated military wing. It originated in 1987 after the beginning of the first intifada, or Palestinian uprising, against Israel's occupation of the West Bank and Gaza Strip.
Hamas is designated a terrorist organisation by Israel, the US, EU, Canada and Japan due to its long record of attacks and its refusal to renounce violence. Under the group's charter, Hamas is committed to the destruction of Israel.
Hamas originally had a dual purpose of carrying out an armed struggle against Israel - led by its military wing, the Izzedine al-Qassam Brigades - and delivering social welfare programmes.
The group nevertheless continued to struggle under the joint blockade imposed on Gaza by Israel and Egypt, and became increasingly isolated after falling out with regional powers in the wake of the Arab Spring. The overthrow of Egyptian President Mohammed Morsi, a key ally, in July 2013 was a further blow.
In April 2014, Hamas agreed a reconciliation deal with Fatah that led to the formation of a national unity government.
Israel held Hamas responsible for all attacks emanating from the Gaza Strip, and has carried out three major military campaigns in Gaza - Operation Cast Lead in December 2008, Operation Pillar of Defence in November 2012 and Operation Protective Edge in July 2014.