After WW II, the international community decided that "no, that's not how wars work any more."
Evolution of Territorial Conquest
“Conquest is not gone, but it has changed. The International Relations field continues to grapple with the question of why interstate war, particularly high-intensity war and great power war, declined after 1945. This study does not settle that fundamental question. Whatever the reasons, these forces extended into the territorial realm and gradually transformed the nature of territorial conquest. As the fait accompli became the predominant strategy of conquest, the most war-prone form of conquest (entire states) declined first, immediately after 1945. Then the intermediate form (populated territories, garrisoned territories) declined around the 1980s. The least war-prone form of conquest (unpopulated territories, undefended territories) persisted. Territorial conquests have not gone away, but rather they have become smaller, more targeted, and less violent.
Small territorial seizures that usually do not lead to war matter more than it may at first appear. Conquest remained the primary initiating event for wars after 1945 and even after 1975. There is tension but not a contradiction between a behavior usually not leading to war and that same behavior instigating most wars. War is rare and becoming rarer. Non-territorial interstate war has never been common. Consequently, despite the increasingly war-averse nature of conquest attempts, they remain central to the causes of most interstate wars. Consider, for instance, the nightmare scenario of nuclear war. To date, a pair of nuclear powers have fought each other with significant casualties on two occasions: China and the Soviet Union over Damansky Island in 1969 and India and Pakistan over Kargil in 1999. Both conflicts began with a military deployment to seize a small, unpopulated border territory.
Looking to the future, the most plausible scenarios that culminate in armed conflict between China and Japan begin with the disputed Senkaku Islands, which remain unpopulated and undefended. China’s disputes with the Philippines, Vietnam, and Malaysia over the Spratly Islands raise similar fears despite the small garrisons stationed there. Although the potential for a Chinese invasion of Taiwan continues to loom, a more limited Chinese seizure of Taiwanese islands like Kinmen, Mazu, and Itu Aba better fits the mold of modern conquest. Similarly, enduring disputes surrounding China’s border with India – often over remote unpopulated areas – linger as a potential source of conflict. The 2017 Doklam crisis could be illustrative of events to come. Elsewhere, the specter of future Russian territorial advances in Ukraine, Georgia, Estonia, and beyond now compete with terrorism at the top of the European security landscape. Territorial conflicts remain common in regions with newer borders, including the Middle East and Africa.”
