What is strategic ambiguity? Here are a few examples. The United States maintains a policy of strategic ambiguity with respect to Taiwan (Haass & Sacks 2020). Israel maintains a policy of strategic ambiguity with respect to its nuclear weapons status. Strategic ambiguity is a policy where a state leaves purposefully vague how it might respond to another state’s behaviour. This vagueness creates uncertainty as well as ambiguity in the mind of the party the policy is directed at. Ambiguity leaves a state purposefully uncertain about another state’s policy.
Ambiguity makes it more difficult, perhaps impossible to calculate risks by creating Knightian uncertainty. A policy of strategic ambiguity may also leave ambiguous not just the probability but also the type of policy response. This makes it even harder for the other party to predict the policy response. Usually, a policy of strategic ambiguity aims to have a deterrent effect by making it difficult, perhaps impossible to calculate the expected costs and benefits of an action. In the case of Taiwan, whether or not the US will come to the defence of Taiwan in the event of a Chinese attack is meant to deter a Chinese attack on the island. In the case of Israel, whether or not it possesses nuclear weapons is meant to deter an attack by its opponents.
But why would ambiguity be preferable to an ironclad commitment to pursue a certain course of action? For example, why is US ambiguity preferable to an outright guarantee to intervene on behalf of Taiwan in case of a Chinese attack? And what does Israel gain by leaving its nuclear status ambiguous? After all, the US has made less ambiguous defence commitments to other countries in Asia. And both Pakistan and India have been forthcoming about their status as nuclear powers.
Explaining why a policy of strategic ambiguity comes about is different from an evaluation of its strategic benefits. Ambiguity often is necessary; otherwise there may not be an agreement in the first place (Iklé 1964). The Sino-US rapprochement would not have been possible, had it not been for the ambiguous stance towards Taiwan. Had Washington maintained an ironclad Taiwan security guarantee, no agreement would have been reached. An ambiguous formulation was necessary to make the so-called third communique possible. Sometimes ambiguity may also be advantageous in terms of avoiding international criticism. This may have contributed to Israel’s decision to maintain a policy of strategic ambiguity. A state can then largely avoid the costs of dis-ambiguity, while largely reaping most of its benefits. Israel’s opponents are unlikely to risk all-out war even if there is only a slight chance of Israel retaliating with nuclear weapons. (In fairness, Israel’s policy is called ambiguous. But it is its official policy rather than its de facto nuclear status that is ambiguous.)
What are the strategic benefits of strategic ambiguity relative to dis-ambiguity? Let’s start with some game theory. Threats and promises aim to alter the other party’s expectations of the issuing party’s future actions. Promises commit one to reward the other party and threats threaten to punish it in the event of pre-specified actions. In order for promises and threats to be effective, they need to be credible. There are different mechanisms to enhance the credibility of one’s commitments (e.g. doomsday machine in Dr. Strangelove). This is particularly useful when a threat may not appear to be credible. For example, the US threat to retaliate against the USSR in case of a Soviet conventional attack on Western Europe was thought to lack credibility. After all, the USSR could legitimately doubt that the US would be willing to provoke a devastating attack on the United States in an attempt to defend its European allies by attacking the USSR. Thomas Schelling famously introduced the notion of a “threat that leaves something to chance” (Schelling 1960). Such a threat is credibility-enhancing. Similarly, the doomsday machine increases the credibility of nuclear deterrence. An unambiguous, irreversible commitment to pursue a course of action conditional on the action of the party is precisely what enhances credibility. This has its obvious problems.
Dis-ambiguity may create a stronger deterrent effect than ambiguity provided the relevant commitments are credible. But it also forced the party pursuing a policy dis-ambiguity to make good on its threat, lest it loses credibility. If the stakes as well as the risk of misperception and miscalculation are high, this is a policy a state may not want to adopt. This is of course one of Schelling’s major insights: credibility can be increased by reducing flexibility.
A corollary is that ambiguity makes it more difficult to undermine the other party’s credibility. At the same time, it affords the opponent an opportunity to adopt salami (or cabbage) tactics that make it more challenging for the deterring party to respond. If the lines are not explicit, the other party may probe. The probed party has less of a credibility problem due to a lack of explicit commitments. But if it maintains a general instead of a specific commitment, it risks a weakening of its position if it fails to push back. Commitments, credibility and flexibility are closely inter-linked.
By limiting the role of credibility, ambiguity provides flexibility at the cost of reduced deterrence. Nonetheless, leaving one’s opponent guessing can be a sufficiently powerful tool to put in place a sufficient level of deterrence, even if explicit deterrence is more powerful. The problem with ambiguity is that a policy of ambiguity may be perceived as an unwillingness to enter commitments and therefore as strategic weakness. Much depends on the degree to which the opponent is risk averse. If very risk averse, ambiguity will probably work. If adventurous, ambiguity may help bring about the conflict that was meant to be avoided. This is where psychology prevails over rationality. Sherlock and Mycroft Holmes understood this difference.
The questions of ambiguity, credibility and flexibility are relevant in the context of the emerging Sino-US antagonism. China and the US look like two freight trains that are inexorably moving towards each other (Allison 2017). Both sides have laid down some red lines (e.g. China vis-à-vis Taiwan independence; US vis-à-vis its commitment to come to the defence of Taiwan). With regard to the more immediate friction in the East and South China Sea, however, the US seems to have avoided (or failed) laying down red lines. Both China and the US have taken to ignoring or at best protecting other’s action (e.g. island building vs freedom of navigation operations). Neither side has drawn a (explicit) red line and continue to pursue a policy of ambiguity. While this may help avoid confrontation, it also allows for a further deterioration of the situation in the sense that both sides will continue to push their policies absent unambiguous and credible red lines laid down by the other side. Ambiguity offers both sides a degree of tactical flexibility. Yet it also fails to stabilise the situation by drawing unambiguous red lines that might lead the conductor to bring the freight train to a stop rather than steer it towards collision.
This is a highly reductionist account of emerging Sino-US competition. It nonetheless offers insights worth exploring further. After all, was it not the existence of – for the most part – red lines that contributed to the relative stability of Cold War superpower competition? Food for thought.