Israel's Hammer Blow in Gaza

Israel's hammer blow against Hamas in the Gaza Strip bears all the hallmarks of its doctrine of overwhelming force. But it was immediately met with calls of defiance from Hamas and warnings that the onslaught would lead to all-out war.

Observers and analysts described it as the largest and most intensive air attack on Gaza since the second intifada erupted in 2000. Israel insisted it was a defensive response to an escalation of militant rocket attacks into its territory.

The bomb and missile strikes by F16 warplanes this morning hit Hamas compounds and positions from Gaza City to Khan Yunis in the south of the coastal strip. Civilian casualties, on a normal school and working day, must have been inevitable in the densely populated area.

Israel's decision to hit what it called "terrorist infrastructure" reflects a deep reluctance to mount large-scale ground operations in the narrow coastal strip, home to 1.5 million Palestinians. Israeli spokesmen claimed that the casualties – reported to include up to 150 fatalities and 400 injured – were Hamas fighters.

Retaliatory Palestinian fire killed one woman in southern Israel – underlining the unequal military balance.

The attacks followed a decision by Israeli prime minister Ehud Olmert's security cabinet to widen reprisals for cross-border rocket attacks on Israel, which began again after the expiry of a shaky six-month ceasefire just over a week ago.

Hamas leaders can hardly have been surprised by the aerial onslaught. Israel's foreign minister, Tzipi Livni, warned clearly and publicly in Cairo on Thursday that Israel "cannot tolerate" continuing attacks after about 50 rockets or mortars were fired from the Gaza Strip.

Livni's high-profile visit to Egypt was seen as part of an Israeli diplomatic offensive to prepare the ground for an attack. But mixed signals confused the picture: Israel also briefly reopened the border crossings into Gaza to allow the delivery of urgently needed fuel, food and humanitarian supplies in the face of mounting international protests at the effects of the continuing blockade.

And there was immediate outrage at the raids from Egypt and condemnation too from the Palestinian Authority, Hamas's bitter rival based in the West Bank town of Ramallah. The authority is backed by the west and has been negotiating with Israel since 1993. Mahmoud Abbas, the Palestinian president – and Israel's partner in slow-moving peace negotiations – condemned it as a "cowardly massacre".

Abbas had been hoping that his negotiations with Israel would acquire new momentum once Barack Obama takes office as the US president and engages with the near-moribund peace process in January.

But opinion polls shows that Binyamin Netanyahu, leader of the rightwing Likud, is likely to beat Livni's centrist Kadima party in Israel's elections, set to take place in February. Prospects for revived talks, which were already slim, must have now diminished further.

Both Livni and Netanyahu have pledged to work to bring down Hamas, which has controlled Gaza since the summer of 2007, two years after Israel unilaterally evacuated its settlements and withdrew its forces.

Israeli officials portray Hamas as a tool of Syria and Iran – both of which do support it – but play down the sense in which it has acquired support and legitimacy because of the serial failures of the PLO, not least in the lack of progress after 15 years of negotiations with Israel.

The looming general election is another reason Israel is not keen to send troops into Gaza on a large scale, which would expose its own forces to heavy casualties. Instead Israel prefers to use its unchallenged aerial superiority – clearly a blunt instrument that cannot distinguish between fighters and civilians.

In carrying out today's raids, Ehud Barak, the hawkish defence minister, is likely to be acting on intelligence pointing to differences between the Hamas political and military leadership.

It is hard to gauge Hamas's popularity in Gaza, but first signs are that the Israeli raids will rally support around it, even if they do, as is likely, temporarily limit its capacity to fire rockets and mortars across the border.

"This is nothing short of a massacre, an outrage," the independent Palestinian MP Hanan Ashrawi – no friend of the Islamists – told the BBC from her Ramallah home. "The cycle of violence is generated by the occupation and by the ongoing state of siege that is attempting to collectively punish a whole people.

"This will enhance the standing of Hamas. People are sympathizing with Hamas as the people who are being ruthlessly targeted by Israel. They are seen as victims of ongoing Israeli aggression."