JERUSALEM - Israel's air attack on the Gaza Strip on Saturday could signal a return to a much higher level of violence in the conflict with Palestinian Islamist group Hamas after nine months of lower-level confrontations.
The peace process with Israel, already in a coma in the last days of George W. Bush's presidency in the United States, could be killed off by renewed violence.
Several factors point to the likelihood of violence worsening following a series of Palestinian rocket attacks since Hamas ended a ceasefire just over a week ago.
* Israel's Defence Ministry signalled it was ready to pursue and widen actions against Hamas in Gaza, including targeting the militant group's leaders, and made clear it was preparing for a potentially long campaign.
"We face a period that will be neither easy nor short, and will require determination and perseverance until the necessary change is achieved in the situation in the south," Defence Minister Ehud Barak said.
* The mayor of Ashkelon, the Mediterranean coastal city in range of Hamas's Grad rockets, said he was told by Israeli military planners that the operation would last for "more than a week".
* Israeli military analyst Ron Ben-Yishai said the strike was "shock treatment ... aimed at securing a long-term ceasefire between Hamas and Israel on terms that are favourable to Israel". It was meant to make it clear to Hamas that Israel would respond "disproportionately" every time rockets harm Israelis.
Ben-Yishai foresaw a rain of rockets on southwestern Israel and "on a wider front, we can assume that Hamas will attempt to dispatch members ... to carry out suicide attacks in Israel".
* Hamas quickly vowed revenge, ordering "all fighters to respond to the Israeli slaughter". It did not say what form this action would take but one fighter maddened by the sight of the mangled bodies of his comrades said suicide bombers would blow themselves up in Israeli restaurants, cafes and streets.
Hamas leaders left the door open to a strong response, saying their movement was popular and deeply rooted. "All options are open to the Palestinian resistance to strike the Zionist enemy," a statement said. "One leader will be replaced by a hundred leaders."
* Islamist fighters fired a salvo of rockets into Israel, killing one Israeli. The mostly homemade, inaccurate rockets have caused few Israeli casualties in the past two months but militants could fire longer-range rockets which can reach the Israeli coastal city of Ashkelon.
* Israeli Foreign Minister Tzipi Livni, who hopes to defeat right-wing hawks to become prime minister in an election in February, has said the rule of Hamas in Gaza must be ended because the Islamists will never make peace with Israel.
* The Israeli air attacks caused widespread anger in the Palestinian territories. Palestinian protesters in East Jerusalem, Ramallah and Hebron staged demonstrations and Palestinian President Mahmoud Abbas condemned the attack and called for "this aggression to stop immediately".
* The Gaza Strip is the bloodiest arena in a militarily lopsided conflict. Some military analysts see it as a proxy war between moderate Arab regimes such as Egypt and hardline states such as Iran and Syria, which back Hamas.
Saturday's end to six months of relative calm during an Egyptian-brokered truce propels the Islamists into the frontline of the Palestinian struggle.
A longer battle could marginalise Abbas's Fatah movement and its Western and Arab peace backers.