Crispin Rovere, a PhD candidate at the Strategic and Defence Studies Centre, Australian National University, writes:

This is a great topic of considerable complexity and I thank Sam Roggeveen for inviting debate. I am happy to take up this challenge.

Although Sam's scenarios 2 and 3 both come with drawbacks and risks, on balance scenario 2 (both Israel and Iran have nuclear weapons) serves Israel's interests more than scenario 3 (neither Israel or Iran have nuclear weapons) with one significant caveat: that across the Middle East it remained in perpetuity that only Israel and Iran have nuclear weapons. This outcome is so unlikely, however, that overall it remains in Israel's interests to disarm itself of its nuclear arsenal as part of a nuclear-weapons-free Middle East.

So let us assume that scenario 3 occurs; Israel disarms of its nuclear weapons and for some reason Iran withdraws from any nuclear aspirations. It is true, as Sam suggests, that this would remove Iran's equaliser and compound Israel's conventional superiority for a while. However, a number of strategic dimensions are likely to result from this that would not be in Israel's interests to eventuate.

First, so long as Israel possesses nuclear weapons, potential adversaries must constrain their ambitions regarding Israel's ultimate destruction. Any war of annihilation against the Israeli state is likely to result in the use of Israel's nuclear arsenal, the consequences of which would far outweigh any possible benefit to the aggressor, and therefore potential adversaries are likely to be deterred from such an undertaking in the first place. In a world where Israel had surrendered its nuclear arsenal, ambitions to 'wipe Israel off the map' become an unlikely, but possible, eventuality.

While Israel retains nuclear weapons, any territory gained at Israel's expense is going to be marginal, while any aggressor will still need to overcome the full power of Israel's conventional forces for any minor advance that is achieved. It is likely then, that so long as the possible gains remain small, and the costs and risks remain high, the existence of Israel's nuclear arsenal reduces the probability of a conventional military build-up in the Middle East that could threaten the Israeli state. In other words, so long as Israel possesses nuclear weapons as an ultimate deterrent, it just isn't worth the trouble of competing with Israel's conventional forces.

It is not credible that Iran will launch a pre-emptive nuclear attack against Israel, as there could only be one outcome from this action: the immediate ending of the Persian civilisation. It remains the case, however, that should Iran succeed in developing a credible nuclear deterrent it increases the freedom of action Iran has in arming militant groups like Hezbollah to attack Israel, just as North Korea has been able to sink the Cheonan and shell Yeonpyeong island without retaliation.

The key here, however, is Iran developing a credible nuclear deterrent. History has established an unfortunate belief that the successful detonation of a nuclear device grants any state immunity from foreign intervention. This is a lesson that North Korea has certainly learned watching Qadhafi's demise in Libya. Yet there remains no inevitability to this, except inasmuch as such an intervention against a nuclear armed state has not occurred thus far.

In the case of Iran, Sam has made the point that an Israeli strike will only delay an Iranian break-out capacity, not remove it. What is missed is that, should Iran test a nuclear device without sufficient stockpiles and deliverable warheads then Israel will certainly attack Iran with American help. Israel has repeatedly stated it will not live with a nuclear armed Iran; so that scenario is quite explicit.

With respect to the actual use of nuclear weapons, the calculation between Israel and Iran is clearly different. Israel would resort to nuclear weapons only after its conventional forces have been overwhelmed and the state appears lost. No comprehensive degrading of Israel's nuclear capabilities can succeed without at the same time threatening the existence of the Israeli state. Conversely, since any attack on Iran's nuclear arsenal is likely to occur early on, Iran would have to choose between using its limited nuclear arsenal, in which case they will be utterly annihilated, or lose their nuclear capability while preserving the state and its leadership. Faced with such a choice, Iran is likely to choose the latter; this scenario demonstrating that Israel's position in a bilateral nuclear dyad remains overwhelmingly strong.

The risk is that Iran is not disarmed, either because there is a lack of political will to embark upon another major war in the Middle East, or because Iran somehow develops a credible deterrent capability without detection. If this happens then a cascading nuclear proliferation across the Middle East is likely to occur that is profoundly inimical both to Israel's security as well as that of the broader international community. If an Iranian nuclear capability is allowed to exist, then Saudi Arabia is likely to procure nuclear weapons from Pakistan. Egypt and Turkey may also pursue nuclear indigenous programs, albeit beginning from a low starting base.

The consequences for Israel's security in such an eventuality would be very grave. In a Middle East with multiple nuclear armed states, the chance of a nuclear attack on Israel would be unacceptably high, either due to nuclear terrorism, miscalculation or the uncontrolled escalation of a lower-level conflict. Security guarantees from allies such as the United States are also likely to have little effect as the ability of the international community to intervene militarily in a regional crisis becomes heavily circumscribed.

So in this context Israel's current policy makes sense. Make the costs of Iran's existing nuclear programme painfully high, and launch a military attack should Iran cross the threshold to a nuclear bomb. Yet, in a future where Iran possesses an unassailable nuclear arsenal it would be of the highest urgency to achieve total abolition of both Israel's and Iran's nuclear arsenal as part of a nuclear-weapons-free Middle East.