It is the mechanism that imposes a collective of conditions and pressures that applies significant adversity on individuals or groups within the bounds of the said system. Those with the potential to evolve and prevail are the ones that do not cease to exist. In some cases they even thrive in the said environment. Those who are unfit, meaning those that do not have the potential to transcend current limits and weaknesses are consigned to extinction. This is what is meant by survival of the fittest. Nature itself singles out those that will survive and those that will not.
In the power play of nations, the idea of natural selection is also a reality. Part of this Darwinian concept is the idea that the fitter an organism, there is the greater likelihood that it will dominate the environment it is in. It would be elevated to the status of prey. Lesser creatures will either be prey to those who are greater, or they will evolve and be predators themselves. When examining this environment it is apparent that it is similar to the interaction of foreign policies of modern states.
When the foreign policy of a certain country is forced by circumstance to yield to that of another more powerful state, there is a political kind of predation. Foreign policies are closely reflective of the scheme of natural selection. An example of this is in terms of how countries aligned themselves in terms of which world power. The usual and rational choice for lesser nations is to attach themselves to more powerful states. There are many motivations behind this. However, they all belong to the realm of survival. Countries behave like their people.
In the realm on international relations and foreign policy, lesser states act like prey, they find ways to survive in an environment of many voracious predators. They usually try to establish a symbiotic relationship with one to keep themselves safe from others. This is the basis of many modern-day alliances. As for world powers, they act like predators. They are at the pinnacle of existence and hold a significant amount of power of life and death on many other lesser entities. They remain as such until such that they are also singled out for extinction. A dominant power lasts only so long as no other power exists that exceeds it or that the adversity of the environment does not overcome it.
Foreign policies are nothing more than active manifestations of states to influence their way to survival. If they fail, they fall prey to the many predators in the international arena. Equally enough these predatory entities live off the weaker creatures in the international community. It takes a significant degree of political maneuvering for a country to survive in the international politics of today. This is not unlike the development of a creature in its pursuit of means to evade eradication and to thrive in a hostile environment.