Why some countries become other powers' battlefields

Which country has most often served as the world's "boxing ring" for wars fought by other powers?

Belgium is a strong candidate, but Korea, Afghanistan, Vietnam, and Pacific islands show the wider pattern created by exposed geography between rival powers.

Belgium, Korea, Vietnam, Afghanistan, and several Pacific islands appear as places repeatedly fought over by outside powers. The common risk is geography: a state lying between stronger rivals or across a contested route can become a convenient arena for their wars. Germany's history differs because German forces were often hired into conflicts fought at home rather than the country serving only as an involuntary battlefield. The comparison gives Korea's position between China and Japan a broader strategic frame.