Wars are fought over what countries cannot grow or mine themselves. Oil and gas are the famous cases, but the list extends: lithium for batteries, cobalt for high-density energy storage, rare-earth elements for permanent magnets and semiconductors, fresh water increasingly across the developing world, phosphate for fertilizer, helium for cryogenics and medical imaging. What makes a commodity strategic is rarely scarcity in the crust; it is the concentration of where it can be extracted, refined, or processed cheaply. Resource geopolitics is the study of how these dependencies shape state behaviour — who has them, who needs them, who controls the chokepoints in between, and what each is willing to do to secure access.
The oil century (roughly 1900–2050) has been the master case. Oil is geographically concentrated (about half of proven reserves in the Middle East, more in Russia and Venezuela), strategically essential (mechanized warfare, modern logistics, petrochemicals, fertilizer), and expensive to substitute over short timescales. The result has been a century in which oil-producing states are courted, defended, and sometimes invaded by oil-consuming powers, and oil-transit chokepoints (Hormuz, Suez, Bab-el-Mandeb, Malacca) have been guarded by external navies whose interest in the trade outweighs the local states' capacity. The post-1973 American–Saudi relationship, the 2003 invasion of Iraq, the protection of Hormuz from Iranian harassment, and the geopolitical reshaping caused by the American shale revolution (2008–), which turned the US from importer to net exporter, are all downstream of oil's centrality. The energy transition is now rewriting the map in real time: lithium (Australia, Chile, China), cobalt (Congo, where two-thirds of supply originates), nickel (Indonesia), and rare earths, where China controls roughly 60 percent of mining but nearer 90 percent of processing. That processing near-monopoly is the most-discussed contemporary chokepoint — and one Beijing has begun to wield, restricting gallium, germanium, and rare-earth exports in 2023–24. Fresh water is the slowly-emerging case: the Grand Ethiopian Renaissance Dam on the Nile (Ethiopia–Egypt–Sudan), the Indus (India–Pakistan), and the Mekong (China–Southeast Asia) all suggest water conflicts will be more frequent in the next half-century than the last.
Every major industrial-policy announcement of the 2020s — the CHIPS Act, the Inflation Reduction Act, the EU's Critical Raw Materials Act — is a resource-geopolitics response to perceived dependency, above all on China. The same logic drives the minerals diplomacy now reaching into Congo, Chile, and the deep seabed. Whether the developed world can de-risk its supply chains without crashing the energy transition's economics, and whether the resource-producing Global South can extract better terms from the new dependencies than it did from the oil one, are the two large open questions in this field.