Geography doesn’t just shape a country’s own foreign policy in isolation – it also fuels one of the oldest and most dangerous appetites in international politics: the desire to control territory that isn’t yours. That impulse, and the theories built to explain and justify it, make up the field known as geopolitics.
Expansion Dressed Up as Strategy
Some states, simply by virtue of where they sit, end up in a permanently expansionist posture toward their neighbors – the way American and British influence has historically pressed outward on the countries around them. That pattern shows up again and again across modern history. Israel’s ambitions toward Arab-held territory, China’s long-running border dispute with Tibet and the pull the Himalayan region continues to exert, and the broader jostling of great powers over smaller, weaker neighbors all follow the same underlying logic: whoever controls the territory controls what’s underneath it and around it.
That’s not a coincidence. Geopolitical ambition and natural-resource competition are almost never separate phenomena – resource deposits take centuries to accumulate, and wherever they’re concentrated, someone eventually wants to bring that ground under their own control. India-China relations offer a clear modern illustration, playing out against the backdrop of Soviet-era ambitions that used neighboring states as a “springboard” for extending influence deeper into contested regions. The same basic pattern showed up repeatedly during the Cold War, as Soviet influence extended into Angola, Ethiopia, Yemen, Afghanistan, Nicaragua, and Cuba – a wide arc of interventions united less by ideology alone than by the same old geopolitical instinct to convert geographic opportunity into strategic control.
Two Competing Theories: Sea Power and Land Power
Formal geopolitical theory generally splits along one central fault line: does global power ultimately rest on control of the seas, or control of the land?
The American naval officer Alfred Thayer Mahan made the case for sea power in 1890, arguing that dominance over the world’s oceans and shipping routes was the real key to a state’s supremacy over its rivals. Britain, with its command of global sea lanes, stood as Mahan’s clearest real-world example of the theory in action. It was a persuasive argument in an age when maritime transport dramatically outperformed anything available on land. It has aged less well since: modern industrial and scientific development, especially the growth of highways and overland transport infrastructure, has eroded much of the practical force Mahan’s theory once carried. Sea power still matters enormously, but it no longer holds the singular, decisive status Mahan assigned it.
The rival case for land power came from the British geographer Sir Halford Mackinder, who introduced his famous “Heartland” theory in 1904. Mackinder treated the combined landmass of Europe and Asia – a region roughly three-quarters land and one-quarter water – as a single strategic unit he called the “World Island.” The label is deliberately provocative: strictly speaking, it isn’t an island at all, since no ship can sail around it, but Mackinder used the term to emphasize just how vast and self-contained this Eurasian core really is. At the center of that landmass sits the Heartland itself, a region Mackinder described through a specific set of features: a huge expanse of plain and elevated plateau; a dense network of rivers, some draining into warm seas and others into a frozen northern sea; and a distinctive position bordered by Siberia along its eastern edge, stretching in a continuous band from east to west.
Mackinder’s underlying claim – that whoever controlled this Eurasian Heartland held the key to controlling the World Island, and through it, the world – would go on to influence strategic thinking for the rest of the twentieth century, shaping how great powers thought about everything from railway construction to Cold War containment strategy. Between Mahan’s oceans and Mackinder’s Heartland, geopolitics has spent more than a century arguing over the same essential question: is power ultimately won at sea, or won on land? Most of modern strategic history has been an attempt, by one great power or another, to answer that question in its own favor.
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