Israel accuses Hamas, which formally declared an end to the cease-fire on Dec. 18, 2008. Hamas says Israel broke it, first by refusing to lift the economic blockade on the Gaza Strip in accordance with the cease-fire's terms and, then, by carrying out two armed raids into Gaza, Nov. 4 and Nov. 17, killing 10 Palestinians.
The Islamic Resistance Movement, known by its Arabic acronym "Hamas," was created in 1987 before the first "Intifada" against the Israeli occupation as a more militant, Palestinian offshoot of the Muslim Brotherhood in Egypt. It was originally promoted by the Israeli government as an alternative to the rival Palestine Liberation Organization. It gets much of its funding from Iran, although Hamas members are Sunni Muslim, not Shiite.
Money also comes from Muslim charities in Saudi Arabia and other Gulf states, and from Muslim groups in the United States. It is an active social movement, providing clinics, education and other social services, but its military wing preaches and practices violence, suicide bombing and other acts of terror against Israeli targets.
But some argue Israel itself is responsible for Hamas' rise. Avi Shlaim, an Israeli professor of international relations at the University of Oxford, wrote in the Guardian newspaper:
"In the late 1980s, Israel had supported the nascent Hamas in order to weaken Fatah, the secular nationalist movement led by Yasser Arafat. Now, Israel began to encourage the corrupt and pliant Fatah leaders to overthrow their religious political rivals and recapture power. Aggressive American neoconservatives participated in the sinister plot to instigate a Palestinian civil war. Their meddling was a major factor in the collapse of the national unity government and in driving Hamas to seize power in Gaza in June 2007 to pre-empt a Fatah coup."