Israel calls its longstanding regional struggle with Iran the mabam, or “war between the wars”, reflecting the feeling that it would one day escalate.

Before the Hamas attacks, Israel and Iran already traded blows in the form of long-range strikes around once a week.

But with Israeli troops on the ground in Gaza, there are now clear concerns that the “true” war will soon begin.

Israel and Iran have spent years preparing their militaries for just such a conflict, but the distance between the two countries continues to pose practical challenges.

The idea of Iran sending large forces through Iraq and Syria directly to join the fighting is currently far-fetched, with any attempt (even if logistically possible) likely facing annihilation from both Israel and the US.

For now, Tehran therefore has three more practical ways to escalate.

The first and most obvious way is through the so-called “axis of resistance” - proxy groups, supported by the Qods force of the Iranian Revolutionary Guard Corps (IRGC).

These proxies vary from almost defunct cells in Saudi Arabia and Bahrain through to ones that are heavily armed and control a great deal of territory – the Houthis in Yemen, and Hizbollah in Lebanon (plus, of course, Hamas).

Groups in Syria provide Hizbollah with support, and the country is a key supply line, which is one reason Israel keeps striking targets there. Iraq also forms a focus, although actions by groups there have mostly targeted US interests.

Took observers by surprise

So far, only two proxies have directly supported Hamas – the Houthis with drone and cruise missile attacks up the Red Sea, and Hizbollah engaging at a comparatively low level across the border with Israel.

The Houthi use of drones was expected, but the revelation that the group had a significant number of longer-range cruise missiles took many observers by surprise.

As shown during a parade in Sanaa just a month ago, they also have increasingly capable ballistic missiles and Israel will rightly be wary of further attacks from this direction.

Hizbollah, though, is the main threat. The group has built up a rocket arsenal believed to comprise up to 100,000 units – many times more than Hamas, and with much greater capability.

With a claimed 25,000 regular fighters and another 25,000 reserves, it is over 50 per cent larger than the forces in Gaza, with significant Syrian combat experience.

Hizbollah has therefore been Israel’s largest concern, in part explaining why the risk from Hamas was overlooked.

The strong IDF deployment to the north has negated the threat of a surprise incursion, and a ground attack would be costly for Hizbollah. Instead its advantage lies in utilising rockets and actions along the border to draw Israel into the difficult and well-prepared defensive terrain of southern Lebanon.

Since the rockets cannot be solely stopped from the air, conflict with Hizbollah would require a sustained commitment from the IDF, on top of operations in Gaza. This two-front war is the best way for Iran to help Hamas. Washington is well aware of this and for Israel the growing US presence is a powerful bolster, designed in part to constrain any such escalation.

The second option for Iran is to accelerate actions by the sophisticated covert global networks of the IRGC. The impacts of these cells are more subtle, but they already play a vital role in helping to drive anti-Israeli sentiment, and more violent actions against Israeli interests remain likely.

Within this realm also lies the threat of enhanced cyber operations against Israel and its interests, with Iran being one of the more competent global cyber threat actors.

The final and most overt way for Iran to strike is through its long-range drone and rocket forces.

The IRGC operates the largest and most diverse missile arsenal in the Middle East. US Central Command estimates a stockpile of around 3,000 missiles.

Around nine of 25 operational Iranian designs have the range to reach Israel, carrying warheads of 500-1,000 kg (these are widely regarded as being nuclear-capable, although Iran currently lacks warheads).

Some cruise missiles also now have the capability to be effective in direct attacks from Iranian territory.

Range, capacity and accuracy of systems has been a major priority for Iran since 2015, although claims of hypersonic weapons capable of avoiding defences are likely over-hyped.

Israel will counter ballistic missiles, including possible launches from Yemen, with the Arrow system but these are a much higher-order threat than the weapons from Gaza.

Alongside or as a more deniable alternative to missile strikes, the Shahad 131 and 136 drones have proven highly cost-effective in Ukraine. In many ways, the best direct escalation option for Iran is perhaps to use the latest iterations of these systems to provide an enduring threat at low cost while maintaining deniability.

This is, ironically, similar to the way in which Israel has been striking back at Iran. Drones have targeted Iranian weapons programmes as well as regional proxies, underscoring the effectiveness of this tactic when conducting conflict at arm’s length.

Such operations will continue, but the Israeli Air Force, supported by submarine-launched cruise missiles, is the main arm of potential retaliation.

Israel has a dedicated cell focused on identifying strike targets for the IAF, likely linked to weapons development, the nuclear programme, and potentially Iran’s leadership.

This mission has been rehearsed with mounting intensity since May 2022, with recent exercises focusing on integrating the F-35 stealth fighter into long-range strike operations.

Stealth helps with, but does not totally negate, the main challenge – the sheer range of the mission, which requires flying over neighbouring states and potentially refuelling twice.

Repeated strikes would be required

Maintaining surprise will be hard, and tankers represent a single point of failure for a long-range strike against Iran.

Moreover, repeated strikes would be required to achieve any significant impact, since targets are widely dispersed and heavily protected. This would be a difficult and costly mission that would be embarked on only by necessity, particularly given that the IAF is already busy closer to home.

Any attack on Iran would also highly likely rely on significant US support to be successful, precipitating wider destabilisation.

Strikes against missile launches from Yemen are, however, more likely, and are well within Israel’s capabilities, serving as an indicator of intent as part of an escalation pathway.

This all suggests an acceleration of previous trends between the two powers rather than a radical departure.

For Iran, this is not yet an existential conflict, and continuing to act through proxies limits the chance of US engagement alongside Israel – something that could actually threaten the regime.

For Israel, direct Iranian involvement would certainly be seen as an existential threat, and would elicit a hard – albeit costly – response.

Israel, then, is similarly better placed in the short term to focus on regional threats, preparing for a two-front war closer to home while seeking to keep Iran at bay through more targeted operations and the growing US force presence. However, this only holds true as long as this conflict does not see an unexpected turn – which is perhaps more than we can expect, given the trend since October 7.

Justin Crump is a British Army veteran, author, and CEO of the strategic intelligence company Sibylline.