As the shadow war between Iran and Israel risks morphing into a direct ‘state-on-state’ conflict between the two countries, Israel’s friends and allies are unanimous in counselling restraint.

Cruise missiles on the background of the flag of Iran.

Yet we now know that an Israeli response will be forthcoming. While Iran’s large scale drone and missile attack was an abject failure, with only 1 per cent evading interception, Benjamin Netanyahu’s war cabinet seems determined on some sort of retaliation. While the US has made clear it will not involve itself in any Israeli attack on Iranian territory, there is one scenario which would force President Biden to intervene: incontrovertible evidence of Iran having crossed the threshold into becoming a nuclear weapon state. For the US and Israel, that is a red line.

Under the terms of the nuclear deal negotiated in 2015, the JCPOA, Iran agreed, in exchange for the lifting of sanctions against it, to reduce its nuclear facilities and accept international monitoring to ensure compliance. Tehran promised to reduce by two thirds its number of centrifuges – essential for enriching uranium – for 10 years (i.e. until 2025), and for 15 years to enrich uranium only up to a level suitable for civil use and nuclear power generation.

In 2018, President Trump withdrew the US from the agreement, claiming it was “a horrible one-sided deal … that didn’t bring peace and never will”. In retaliation, Iran resumed its nuclear activities. Within two years Tehran had cut in half the time needed to produce enough weapons-grade fuel for a nuclear bomb. David Albright, president of the US Institute for Science and International Security recently assessed that “Iran can make a crude nuclear explosive in about six months, would need a year to build a semi-reliable [nuclear] warhead…and about two years to have a fully developed nuclear weapons production complex”. The events of the last few weeks will have prompted Iran to accelerate this timetable even further.

This faces Israel with a genuinely existential threat. If Iran managed to get even one nuclear weapon, that could spark a nuclear holocaust. A nuclear-armed Iran would also have devastating consequences for nuclear non-proliferation. Saudi Arabia has long made clear that it would immediately seek to develop a nuclear weapon capacity of its own, probably aided and abetted by nuclear-armed Pakistan. To have three nuclear weapon states (Israel has been an undeclared nuclear weapon state for decades) in the world’s most volatile region increases the chances of a nuclear war by several orders of magnitude.

That is why some are wondering whether Israel’s retaliatory strike will focus on Iran’s nuclear arms manufacturing infrastructure. It would make logical sense. But it bears repeating that there are very real military and political difficulties in doing so.

Iran has taken good care to keep its nuclear enrichment facilities deep underground, where even the most penetrative bunker-busting bombs could struggle to have an impact. Then there is the political cost of such a move. An attack like this, even if unsuccessful, would certainly prompt a further Iranian response directly and through its proxies in the “ring of fire” around Israel. This would include the extremely well-armed Lebanese Hezbollah who have been carrying out daily skirmishes with Israel during the latter’s war with Hamas. Amid such an attack, with missiles fired from Lebanon, Yemen, Iraq, and Syria, could Israel’s Iron Dome once again keep over 90 per cent of the projectiles at bay? Regardless, it would risk a region-wide war.

Whilst this apocalyptical scenario may not materialise, it is vital to remember at moments like this that we have sleepwalked into disaster before. Ultimately, bombing Iran’s nuclear facilities risks serious escalation. But allowing Iran to develop a nuclear bomb leads to a geopolitical disaster. As we approach a nuclear tipping point, the stakes have rarely been higher.