[mikeash]

Is official policy important? If China or Russia or whoever decide one day that they need to make a first strike against population centers, it's not like they're going to say, "oh, I wish we could, but we can't, it's against policy."

[jwtadvice]

Yes official policy is important. This is for several reasons:

1. Official policy communicates expectations. Others derive their behavior from, in large part, the official positions of others.

2. Official policy provides a mechanism of commitment. It is difficult to withdraw from or engage in something that is against public and officially stated policy (in both domestic politics and international relations).

3. Official policy is a mechanism to inform and constrain other national choices. It is difficult to have multiple official policies that clearly contradict, such as having an official policy of dismantling all nuclear arsenals at the same time as having an official policy to provide a nuclear umbrella over protectorates. When administrations transition and when new staff come into security planning, their choices on other policies are constrained by existing policies.

4. Cultivating an expectation that official policy is a good predictor of behavior provides a strong signaling function to other states, and for the building of statecraft. Countries that have no credibility often have none because of their misalignment of actions and official policy.

But yes, nations do sometimes decide to change policy or act against their policy. In the case of Russia or China as you've written in the above comment it is very highly unlikely for a large number of reasons. But it remains possible in slim margins, sure, and could be fun to speculate about.