If there is a peculiarity about this campaign, it is in its aura of incoherence, says Peter Beaumont

Military operations have their own logic. A point is reached where circumstances, political and military, drive the dynamic and can overwhelm the original intention of the combatants.

On Saturday, as Israeli armour gathered close to Gaza's border for an expected invasion after days of aerial bombardment, hope seemed to be rapidly diminishing that a wider war could be avoided.

It is tempting to compare the current military operation to the one launched against Gaza four years ago, which I covered in Israel and later in Gaza. What was striking was the unanimity across a mobilised Israeli society and the perceived clarity of objectives – ultimately not to be achieved.

A lot has changed in four years. Hamas, which had rearmed, has learned lessons from the last conflict, aware that in a ground war it will be given little quarter, which gives it little incentive at this stage to back down. Neither is it unaware of the fear and damage it can spread with its longer-range missiles aimed at Israel's cities. Casualties, two months before Israel's elections, are a political issue.

Governments once sympathetic towards Israel, including the regional powers Turkey and Egypt, have been drawn closer to Hamas, which cannot be unaware of the opportunity the Israeli attack offers it in political terms.

On Israel's side too, the room for manoeuvre is fast closing. The defiance of Hamas after the assassination of its military leader, Ahmed Jabari, and scores of airstrikes has meant that, even if Israel had intended this to be a limited operation, it is now bound by its own logic of escalation.

If there is a peculiarity about this campaign, however, it is in the aura of incoherence surrounding it. The message coming from Israeli prime minister Binyamin Netanyahu and his inner circle often seems confused. Even as cabinet ministers were vowing to push ahead with the second phase, the Jerusalem Post reported a phone call from Netanyahu to US president Barack Obama in which it said they discussed "de-escalation".

Part of the problem has been in assessing what Netanyahu desires. Denying that the intention is to topple Hamas, that leaves only the possibility of degrading its weapons and capacity, which, as Israel's war against Lebanon in 2006 – as well the 2008 operation – demonstrated, has only a limited utility. Indeed, both Hamas and Hezbollah, after rearmament, emerged with more powerful arsenals.

The reality is that Netanyahu's favoured tactic as a politician over his long career has been about not making things happen but preventing them, a tactic he has pursued assiduously in his prickly relations with Obama that has all but shut down the peace process.

The timing, as the veteran Israeli peace campaigner Gershon Baskin points out, has been peculiar. Baskin, who helped to negotiate the release of kidnapped Israeli soldier Gilad Shalit and communicated through an intermediary with Jabari, alleges that Jabari was preparing to sign a formal ceasefire plan when he was killed.

It is this that has led to allegations, including from Palestinian Authority president Mahmoud Abbas on Friday, that Israel launched its assault with the object of undermining Abbas's efforts to secure a diplomatic upgrade at the UN this month. Others have suggested the dynamics of Israel's domestic politics – it holds elections in January – as another factor.

Whether Netanyahu has not thought it through, or whether his thinking is coloured by a different agenda, the stakes he is playing for have been dramatised starkly in the last five days.

Although support for Israel remains strong in Washington and European capitals, in a Middle East transformed by the Arab spring support for both Gazans and Hamas has been intensified in the governments of Tunisia, Egypt and Turkey – all US allies. Qatar, too, another Washington ally that has emerged as an increasingly important player and offered to invest heavily in Gaza only last month, has also been infuriated, demanding that Israel be "punished". For his part, Turkey's prime minister, Recep Tayyip Erdogan, on Friday depicted the attack by Israel as a pre-election stunt.

While the consequences might not be obvious in the short term, it will complicate both US foreign policy and isolate Israel, a fear already being expressed within Obama's inner circle. According to the New York Times, US officials are fearful that an Israeli invasion could backfire politically, pushing Palestinians closer to Hamas and damage Israel further in the region.

The rising sense of crisis over Gaza has been underlined by warnings from unnamed US officials that Egypt's president, Mohamed Morsi, who has avoided populist gestures so far, would be pushed to the brink by an invasion.

Something dangerous has been unleashed at a time of growing regional instability and lack of international engagement. What has been let out of the box can not easily be put back.