Donald Trump fails the Caroline Test of “imminent attack” because inaction was risky

One person’s target of opportunity is another’s “threat of imminent attack”.

The terms “anticipatory self-defense”, “preemptive self-defense” and “preemption” traditionally refers to a state’s right to strike first in self-defense when faced with imminent attack.[3] In order to justify such an action, the Caroline test has two distinct requirements:

  1. The use of force must be necessary because the threat is imminent and thus pursuing peaceful alternatives is not an option (necessity);
  2. The response must be proportionate to the threat (proportionality).[4]

In Daniel Webster’s original formulation, the necessity criterion is described as “instant, overwhelming, leaving no choice of means, and no moment of deliberation”. This has later come to be referred to as “instant and overwhelming necessity”.[5][6]


Thus the destruction of an insignificant ship in what one scholar has called a ‘comic opera affair’ in the early 19th century nonetheless led to the establishment of a principle of international life that would govern, at least in theory, the use of force for over 250 years.[1]…

This incident has been used to establish the principle of “anticipatory self-defense” in international politics, which holds that it may be justified only in cases in which the “necessity of that self-defense is instant, overwhelming, and leaving no choice of means, and no moment for deliberation”. This formulation is part of the Caroline test. The Caroline affair is also now invoked frequently in the course of the dispute around preemptive strike (or preemption doctrine).[6]…