Why do nations behave as they do? This question is the pivot of foreign policy.
International affairs has two major analytical viewpoints. The first is Idealism, which typically involves a value-based analysis of the world. There are good guys and bad guys and we support the good guys. The work of Woodrow Wilson to establish a moral approach to foreign policy following the First World War is an example of the type, and so is the neo-conservative approach of George W. Bush or Ronald Reagan's "evil empire" approach to the Soviets.
The second is Realism, a viewpoint that specifically subtracts moral viewpoints from foreign policy. Instead, Realism elevates national interest and security above ideology, moral concern or social engineering. This school goes back to Sun Tzu and Machiavelli, and includes the balance of power of Bismarck, the realpolitik of Henry Kissinger, and - arguably - the current policies of Barack Obama.
In his book, The Next 100 Years, realist thinker George Friedman lays out what he calls the "Grand Strategy" of the United States. This is the overriding series of goals that must be achieved to maintain American power, domestic peace and high standards of living. It is a strong example of Realist thinking that coldly calculates the factors necessary in national security, rather than what would be nice.
The list can summarized as:
1. U.S. Army controls the continental United States.
2. Naval control of the approaches to the continental United States.
3. No rivals in the Western Hemisphere.
4. Control of ocean trade routes in the rest of the world.
5. Preventing the rise of a rival hegemonic power, particularly in Eurasia.
The first step is an absolute necessity to U.S. security: control of the heartland itself. Each step builds off of the first other in sequence. So military control of the continental United States allows control of the naval approaches to prevent a foreign invasion. Control of the approaches to the United States allows the containing and destabilizing of hemispheric rivals. And so on.
Friedman describes the U.S. grand stategy a bit on his website:
"The United States operates with a grand strategy derived from the British strategy in Europe - maintaining the balance of power. For the United Kingdom, maintaining the balance of power in Europe protected any one power from emerging that could unite Europe and build a fleet to invade the United Kingdom or block its access to its empire. British strategy was to help create coalitions to block emerging hegemons such as Spain, France or Germany. Using overt and covert means, the United Kingdom aimed to ensure that no hegemonic power could emerge.
The Americans inherited that grand strategy from the British but elevated it to a global rather than regional level. Having blocked the Soviet Union from hegemony over Europe and Asia, the United States proceeded with a strategy whose goal, like that of the United Kingdom, was to nip potential regional hegemons in the bud. The U.S. war with Iraq in 1990-91 and the war with Serbia/Yugoslavia in 1999 were examples of this strategy. It involved coalition warfare, shifting America's weight from side to side and using minimal force to disrupt the plans of regional aspirants to gain power. This U.S. strategy also was cloaked in the ideology of global liberalism and human rights.
The key to this strategy was its global nature. The emergence of a hegemonic contender that could challenge the United States globally, as the Soviet Union had done, was the worst-case scenario. Therefore, the containment of emerging powers wherever they might emerge was the centerpiece of American balance of power strategy."
Friedman states that all countries have a grand strategy, verbalized or unacknowledged, achieved or impossible. Many actors in the state, even at a high level, can ignore or remain unaware of this analytical framework, but it is there nonetheless, guiding decisions that may otherwise be perplexing to understand.
As the same time, achievement of even the first step of a grand strategy is not a given. Belarus has a multi-step grand strategy that likely begins with maintaining integrity of their borders and independence from rival powers. But the political and economic dominance of that country by Russia compromises even the first step.