The conflict between the Israeli Defence Forces (IDF) and Hezbollah in south Lebanon has slipped up a couple of gears since Israel’s coup of the exploding pagers and walkie-talkies a week or so ago.

The IDF quickly followed up that particular triumph with an intense aerial bombardment of the terrorists’ positions and fighters, and all the indications are that Hezbollah has been hit hard. They are very much on the back foot, reeling from the onslaught and trying to recover. That may take them some time.

And yet they are not totally defeated. They have had 18 years to prepare for this moment, ever since Israel last withdrew its troops from southern Lebanon in 2006 when the level of its casualties being incurred there became politically acceptable to the Israeli public.

As Hamas has done in Gaza, Hezbollah has used the time to construct a network of tunnels and strongpoints which are difficult, and some well-nigh impossible, to destroy from the air.

So while the IDF continues to attack from the air, and despite calls from outside observers for them to desist, Israel is preparing for a ground invasion which may come in the next few days. Former Conservative MP Tom Tugendhat, previous Minister for Security and a man with some operational experience himself, has said he expects Israel to move in the next 48-72 hours. He may well not be wrong.

Meanwhile at the UN General Assembly meeting in the USA this week there have been numerous calls for peace. The US, France, the UK and sundry others have even proposed a 21 day ceasefire to allow negotiations to be initiated.

This has been rejected by the Israeli government, and Israeli military chief Lieutenant General Herzi Halevi has told IDF troops that they are “preparing the process of a manoeuvre, which means your military boots … will enter enemy territory”. His remarks were published after Israel called up a further two reserve brigades “for operational missions in the northern arena”. The signs are ominous.

If the IDF were indeed to strike into southern Lebanon as seems increasingly likely, what might the main aims of the operation be?

First and foremost will be the continuing degradation and destruction of Hezbollah and its resources. When your enemy is down on the canvas then it’s important not to let him get back up; this is no boxing match under Queensberry rules. It is a fight to let the 60,000 or so Israeli citizens who have left the northern part of Israel to escape Hezbollah’s rocket barrages return home safely.

It will be no easy task. Not only do the terrorists still have a sizeable arsenal despite Israel’s attrition, they will also be skulking in buildings and caves which they have had ample time to prepare defensively, and they will also have the advantage of local knowledge of the terrain. The IDF will have to tread carefully as it winkles them out, much as it has had to do in Gaza although this time in a less urbanised context.

Thereafter it will seek to push the Hezbollah remnants north until they no longer pose quite the same threat to northern Israel, which means essentially beyond the reach of their numerous shorter-range unguided rocket weaponry. Realistically this means beyond the 40 km range of its Soviet-era BM-21 and BM-27 multiple rocket launchers.

This would equate to some distance north of the Litani River in Lebanon, which runs roughly parallel to the Israel-Lebanon border. It has been used as a demarcation line for the cessation of hostilities in previous wars, but Hezbollah always filters south again.

It would involve Israel in occupying a considerable chunk of Lebanese territory and there’s no indication that it would relish the opportunity, but if that’s what it takes to achieve their war aim then it might just be what they have to do. Thereafter both sides would probably be exhausted and welcome peace negotiations.

That’s where we are at the moment. Israel is poised to invade. Hezbollah expects the worst, and its sponsor and ally Iran has declined to join the fray so far. The next few days will be critical.

Lt Col Stuart Crawford is a political and defence commentator and former army officer. Sign up for his podcasts and newsletters at www.DefenceReview.uk