The ongoing Operation Pillar of Defence is the latest manifestation of Israeli efforts to disarm Hamas of its supply of long range missiles and to demonstrate to Hamas' leadership the strategic miscalculation of using force to pursue its objectives.
Operation Cast Lead, the 2008-2009 Israeli air-ground offensive against Hamas in Gaza bought more than two years of relative calm along the Gaza border, with Hamas, Palestinian Islamic Jihad and the Popular Resistance Committee largely refraining from significant attacks against Israel. When attacks were launched, the Israel Defence Forces responded usually with limited and proportionate aerial counter-strikes - a contained but sometimes lethal game whose rules were understood by both sides.
The circle of Israel's taut anti-munitions blockade along its borders and on the coastal margin, despite assurances, was never properly closed on the Egyptian frontier. This allowed Hamas and its allies to replenish - and increase - the arsenal of missiles and other weaponry that had been decimated during Cast Lead. Iran has long played a malevolent role in stiffening the resolve of extremist groups in Gaza to maintain their hard-line against Israel. It continued to do so in the post Cast Lead years; supplying funds, munitions and training. Of particular concern to Israel was the supply of large quantities of Iranian manufactured Fajr-5 long-range missiles, capable of striking up to 75 kilometres. This brought Tel Aviv into Hamas' missile range for the first time, as its citizens have discovered in the past few days.
In recent months Hamas was emboldened by the rise of its ideological counterpart, the Muslim Brotherhood, in Egypt and the restrained Israeli response to its attacks. It dramatically turned intent into action a week ago through a lethal ambush against an Israeli border patrol and the launch of 120 missiles into Israel in two days.
Israel's Strategic Objectives
Thus the stage was set for Operation Pillar of Defence. What are Israel's strategic objectives? We can be sure that Israel is aware that no military campaign will realistically defeat Hamas or create lasting peace with them or the other jihadist groups that operate in Gaza. This can only be achieved by a political settlement; which is nowhere in sight and probably never will be.
Instead Israel intends to re-set its 'game' with Hamas. Its objectives are: a cessation of cross-border attacks, missile launches and munitions smuggling. In particular Israel cannot tolerate Hamas re-arming with long-range missiles that can hit its major population centres. Even without Hamas's recent crescendo of attacks, the Israeli government would have felt obliged to intervene sooner or later to deal with that threat.
It is unlikely that these objectives can be achieved from the air alone. Despite over 1,000 Israeli sorties in the last few days, missile launches from Gaza into Israel continue.
Overwhelming pressure is required against Hamas, from Egypt, the Arab world and from the West, to force them to accede to Israel's demands. It is possible that such pressure might be achieved by a combination of Israel's air operation and the threat it presents by the mobilisation of 75,000 reserves.
But despite Israel's 2008-2009 demonstration of resolve, the question will still be asked in Egypt as to how serious the Israeli government is this time round. Egypt and the Arab League will see the submission of Hamas to Israel's will as damaging to their own prestige, and will not want this to occur unless they believe they have no other choice.
Israel's Tactical Options
It is therefore possible that we will see an Israeli ground offensive in the coming days. Operation Pillar of Defence has concentrated on: destroying missile stocks and storage sites and killing selected members of Hamas' leadership. Those targets, as well as Hamas' rank-and-file fighters, would remain the focus of a ground assault. Israel has made considerable efforts to minimise civilian casualties during its air operation, in particular implementing intensive intelligence and surveillance efforts to support accurate and precise targeting. The IDF has also sent emails, text messages, phone calls, leaflet drops and fired sound munitions to warn civilians away from Hamas positions. Every strike aimed into a populated area is authorised at the highest level within the Israel Defence Forces. Israeli pilots and missile controllers are required to wave off a mission if there is too great a risk of collateral harm.
I would expect such efforts to continue during a ground operation. But in today's world of ultra-smart aerial munitions, ground forces often represent a blunter instrument - both in the context of less sophisticated weaponry and a greater susceptibility for human error among infantrymen, tank crews and artillery gunners. A higher ratio of civilian to combatant casualties can be expected.
And of course IDF ground forces will not enjoy the relative invulnerability of its pilots. Hamas will undoubtedly have made extensive preparations for defence against an Israeli assault, including laying improvised explosive devices, tunnelling and readying suicide attackers.
Israel will have prepared a range of options for a ground war, and would no doubt prefer a short, sharp campaign. Not least, Israel undoubtedly recognises that the present and extensive international support for its operations will likely fracture under the pressure of a ground operation. The stance of global media organisations, generally less hostile to Israel than during Cast Lead, is similarly fragile. But when combat is joined, operations have a tendency to become unpredictable and beyond the control of planners. If launched, the ground war will last until Hamas accepts Israel's demands - and that could be anything between a few days and a few weeks.
The Significance of the Wider Middle East
Egypt remains fundamental to this equation. It will have to play its role in containing Hamas and its weapons supply. President Morsi's influence on Hamas is significantly stronger than was President Mubarak's, as the relationship is much closer. President Morsi depends on Hamas to control the Gaza strip, and will not want to see it decimated. Israel will hope that the relationship between the Muslim Brotherhood and Hamas will lead to ever-greater cooperation after Pillar of Defence, with Egypt taking increased responsibility for the Gaza Strip.
Qatar also is becoming increasingly influential here, as it is elsewhere in the region and beyond. During the Emir's recent visit to Gaza his assertion that the age of the armed struggle is over was met with stony faces by the Hamas leadership. They were more impressed, however, by his intention to invest $400 million. Such funding, no doubt with strings attached, perhaps represents a glimmer of hope that the political leadership of Gaza might focus more attention on economic development and less on a violent struggle that will make a re-run of Pillar of Defence inevitable.
Colonel Richard Kemp is a Senior Associate Fellow at RUSI. He is currently in Israel observing the military dimension to this conflict.
The views expressed here are the author's alone and do not necessarily reflect those of RUSI.