my educated guess is that foreign policy is based on internal factors. Even if policy-makers point to seemingly external factors, the decisions are made by their own perceptions and interests regarding those external factors. Based on realist theories, states (and when i say states, i mean countries) act in their own self-interest based on a perceived power struggle. Although their policy may be gaged by international/external events, it is their perception that makes the policy.
You could say that the "war" in Iraq was started based on a perceived threat. Did Saddam Hussein threaten the US in any direct (or even indirect) way? Not really.
I'm not gonna go much further because I can tell by the description this is straight from some kind of assignment, but you can use this as a starting point.
INTL/POLI class - International Relations