Salami tactics, we can be sure, were invented by a child […] Tell a child not to go in the water and he’ll sit on the bank and submerge his bare feet; he is not yet ‘in’ the water. Acquiesce, and he’ll stand up; no more of him is in the water than before. Think it over, and he’ll start wading, not going any deeper; take a moment to decide whether this is different and he’ll go a little deeper, arguing that since he goes back and forth it all averages out. Pretty soon we are calling to him not to swim put of sight, wondering whatever happened to all our discipline.
The key to salami tactics’ effectiveness is that the individual transgressions are small enough not to evoke a response. As Schelling put it:
If there is no sharp qualitative division between a minor transgression and a major affront, but a continuous gradation of activity, one can begin his intrusion on a scale too small to provoke a reaction, and increase it by imperceptible degrees, never quite presenting a sudden dramatic challenge that would invoke the committed response.
James Fearon showed more formally that this can indeed work: as long as the individual demands are small enough and do not strengthen the future bargaining position of the challenging state (China) too much, then states can resolve those claims without resorting to war (and the challenging state gets much of the sausage).
So how should the United States respond in this case? Schelling suggests that having a reputation for sometimes randomly punishing a minor transgression might help to deter future claims. This is a risky tactic. Instead, the United States appears to have done the predictable thing. As Steve Saideman put it:
So, the US is pretty inconsistent in many ways over the decades, but tell it to shove off and not send its military through a space and you can pretty much count on a visit by the US Navy or Air Force.
At the same time, the United States appears to have given China a sliver of the salami by instructing its commercial airlines to inform Chinese authorities of their flight plans. How dangerous this is depends in part on how far China can really take the strategy of taking very thin slices of the salami. At some point, it will have to do more if its true intent is regional hegemony. For example, physically occupying islands would surely be seen as a discontinuity rather than just setting another foot in the water. As Robert Powell has shown, taking a chunk of the salami can lead to war.
U.S. actions are aimed at discouraging China from taking such unambiguously expansionary steps. Nevertheless, Stephen Walt is right that in the longer run we should be very worried about what will happen between the United States and China.