Iranian nuclear programme may 'inadvertently' trigger military action

Netanyahu red lineIran may inadvertently cross unclear US and Israeli 'red lines' with its nuclear programme and trigger military action, warns a new briefing paper by the Royal United Services Institute (RUSI).

Iran: Red Lines and Grey Areas, written by Hugh Chalmers and Shashank Joshi, argues it is important that all parties - including Iran - understand where war-triggering 'forceful red lines' are located and concludes that Iran's adversaries have set 'poorly conceptualised' red lines with 'significant ambiguity' resulting in confusion.

Although the paper acknowledges that ambiguity is inherent to deterrence and may even be both intentional and unavoidable due to the complexity of the technical and political issues surrounding a nuclear-weapons capability, Chalmers and Joshi warn that poorly understood 'red lines' which are simultaneously pitched at domestic and international audiences, as well as Iran, could result in the Islamic Republic triggering military action by mistake.

'The proliferation of different types of red lines, with widely disparate threats, audiences and purposes, makes it harder for forceful red lines to serve their fundamental deterrent purpose. Amidst a profusion of red lines, forceful ones are at risk of being opaque or even unintelligible to Tehran,' argue Chalmers and Joshi.

However the briefing paper highlights that the US and Israel have struggled to strike a balance between too much and too little ambiguity.

'Red lines that are highly specific about the range of prohibited activities and the promised consequences of transgression might commit Iran's adversaries to disproportionate or ineffective responses, risk losing the element of military surprise, provoke opposition from third parties, and allow Iran to proceed with all activities not expressly mentioned. On the other hand, ambiguous red lines keep Iran guessing but also increase the risk that Iran inadvertently crosses the threshold. Policy-makers would consider it neither feasible nor desirable that all ambiguity be removed - but it is important that they understand the scope and severity of that ambiguity, as it is perceived in Tehran.'

Chalmers and Joshi outline three red lines. The first is the American red line of the production of nuclear weapons or decisions to that end. The second is the Israeli red line of a level of enriched-uranium stocks - the material capable of being turned into bomb fuel - totalling 240 kg, or a bomb's worth. They also examine a third red line that might be imposed in the future: the 'critical capability' red line - based on how quickly Iran can enrich uranium - after which it would be feared that Iran could, undetected, rush a nuclear-weapons capability between stringent international inspections.

In each of these cases, 'Iran may take steps which, in its view, fall short of an articulated red line, yet those steps may conversely be interpreted by the US or Israel as violating, or indicating imminent violation of, that same line.' Importantly, 'Iran might believe that those red lines which have been articulated are comprehensive', but 'Iran's adversaries might assume that other, unarticulated red lines - such as the expulsion of IAEA inspectors from Iran - are implicit, but nonetheless operative.'

'Iran is likely to be able to remain below both the declared US and Israeli red lines in perpetuity (even though, given their ambiguities, this is not certain), as long as it limits its stockpiles of enriched uranium and abjures from any decision to manufacture a nuclear weapon. But its growing enrichment capability may induce the declaration of a capability-based red line, one that might very well be transgressed on current trends,' write Chalmers and Joshi.

'The dilemma is that in the absence of such a red line, the US and Israel might have to accept the status quo, including heightened military readiness and a problematic sanctions regime, for years or even decades to come.'

'But setting such a red line is difficult because the notion of 'critical capability' is highly subjective, and defining that prohibited capability in objective terms (such as the number of centrifuges) might be seen as arbitrary, disproportionate and inflexible. If the latest round of talks do not bear fruit by the late summer, after Iran's presidential elections are concluded, then this issue will become central to the debate on Iran.'

'By one account, over the past fifteen years Iran's nuclear programme has crossed no less than seven so-called 'red lines' set by the United States or Israel. As Iran has crossed these lines, it has incurred the most punitive and protracted countermeasures ever imposed on a suspected nuclear proliferator. But it has not faced conventional military action. More recently, however, the idiom of war-triggering red lines has become widespread and central to the discourse on Iran.'

'These dilemmas and problems exist whether one is an advocate or opponent of red lines and deterrent threats. Notwithstanding the strategic role of ambiguity, it is important that all parties to the dispute - including Iran - understand where forceful red lines are located. At present, and for reasons outlined in this paper, we are far from this point of mutual understanding.'

To read Iran: Red Lines and Grey Areas in full please click here


1. Any enquiries and interview requests, please contact : Daniel Sherman

2. Hugh Chalmers is a Research Analyst at RUSI. For a full biography, please visit

3. Shashank Joshi is a Research Fellow at RUSI. For a full biography, please visit

4. RUSI is an independent think-tank for defence and security. RUSI is a unique institution; founded in 1831 by the Duke of Wellington, it embodies nearly two centuries of forward thinking, free discussion and careful reflection on defence and security

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