For the fifth time in seven days, Egyptian mediators announced yesterday a negotiated ceasefire to end fighting between the bitterly opposed Palestinian groups. But even if the ceasefire holds, it was clear this weekend that Israel planned to use the situation to settle political and military scores with both Hamas and militants who had engaged in a steady bombardment of Israeli towns near the Palestinian borders with their mostly ineffectual homemade rockets.

The announcement of the latest truce also failed to give any details, a bad sign considering that while the fundamental question of who commands the security forces in Gaza remains unanswered, no ceasefire will last, according to almost everyone involved.

An agreement signed by Hamas and Fatah in February to share power collapsed last week, when Interior Minister Hani al-Qawasme resigned because he could not control the various factions of gunmen supposedly under his command.

Al-Qawasmeh had been selected as a neutral choice to lead Gaza's security forces but his neutrality also meant he lacked any gunmen of his own, thus making it impossible for him to exercise any authority over Gaza's many different semi-official armed factions.

Within a day, Gaza blew apart, once again sending masked gunmen to the streets in a flurry of gunfights, hostage-takings and a siege of the Islamic University - the intellectual birthplace of Hamas, and a symbolic and military flashpoint over the past year of conflict between the two parties.

Even as the guns in the Fatah-Hamas conflict began to quiet, Israel responded with an unexpected offensive against Hamas-related targets and officials that Israeli officials have long considered terrorists and not part of a legitimate Palestinian government.

Although the US and Israel have openly supported Fatah in the fight by supplying money, equipment and training to its top military commander in Gaza, Mohammed Dahlan, the Israelis insist that the daily air and artillery attacks on Hamas targets are designed to halt rocket attacks on the small Israeli towns that ring the walled-off Gaza Strip, a narrow sliver of land jammed with nearly 1.5 million Palestinians.

Hamas officials retort that Israel was supporting Fatah, whose fighters appear to be out-gunned, out-trained and out-led by their Hamas rivals. By midweek, Abu Obaida, spokesman for the Hamas military wing, declared an end to the tattered Hamas ceasefire with Israel.

Previously, with a few exceptions, Hamas had been honoring a six-month-old ceasefire with the Israelis and had not been firing rockets itself. But its security forces had also ignored repeated attacks on Israel by rocket teams from Islamic Jihad, a militant group of increasing power which ignores domestic Palestinian politics and internal clashes in favour of attacks on Israel. And Islamic Jihad has refused every overture to negotiate on any aspect of Palestinian-Israeli peace.

As the battles with Fatah broke out across the strip, Hamas quickly entered the rocket-firing fray and the nearby Israeli town of Serdot took damage and casualties. But the Israeli offensive, which targeted not just rocket teams but top Hamas commanders, installations and infrastructure, also left the group reeling as it ordered its men to disperse from all known Hamas installations, stay off mobile phones and avoid large gatherings that could be targeted by superior Israeli military technology. This attack on their opponent's command and control ability, at least temporarily, seems to have saved Fatah from a military defeat and might have set the stage for yesterday's ceasefire to hold longer than the previous attempts.

But Hamas and other militants seem convinced that an Israeli invasion of Gaza is the best plan of action, no matter the cost. In interviews with both Islamic Jihad and Hamas militant commanders over the past month, The Observer learned that both groups badly want to draw Israel into a protected ground combat in a reinvasion of Gaza for political and military reasons.

Politically, Abu Hamza, the top Islamic Jihad commander in charge of the group's rocket programme, told The Observer that the only way to unify the split Palestinian factions is a battle with Israel, even if it devastated the already economically staggering Gaza Strip. And militarily, both Hamas and Islamic Jihad claim to have adopted weapons, training and tactics from Israel's summer war with Hizbollah and are convinced they can repeat the Lebanese militant group's success on the ground.

For its part, Israel is reluctant to co-operate. Prime Minister Ehud Olmert cannot politically afford an open-ended military incursion but remains under heavy military pressure to reduce the rocket attacks and neutralise the growing influence of Hamas. So Israeli troops and air power have greatly increased aggressiveness, while their leaders debate a full-scale incursion that many in Gaza and Israel consider inevitable.

Regardless of whether the ceasefire holds for an hour or for a month and even without Israeli tanks and warplanes settling scores with militants, Gazans face a bleak future