The concept of balance of power is fundamental in international relations. What does it mean?

How meaningful can it be at the beginning of the 21st century, given the impact of globalization and modern warfare in which one's opponents may not be attached to any particular state? Is it possible that it requires redefinition? If so, what should it mean? If not, why not?
What will be an ideal response?

Ideal Answer: The ideal answer should include:
1. Provide a satisfactory explanation of how balance of power is crucial to international relations, employing the key terms military capabilities and dominance.
2. Explain how the complexities created by globalization and modern warfare impact the significance of balance of power, noting the fluidity of alliances and policies necessary when one's opponents may not be attached to any particular state, as well as the increasing emphasis on economic power over military power.
3. Describe the redefinition that such an evolving and evolved role of balance of power appears to demand, taking into account the details already touched upon, and perhaps those elements of future international relations that might require this redefinition.
4. If the concept of balance of power does not appear to require definition, a vigorous analysis of why not will be necessary.
5. Provide a concise and effective conclusion.