Just 18 months ago, many politicians, academics, and experts in the United States and Europe were waxing poetic about the geopolitical benefits of the coming transition to cleaner, greener energy. They recognized that moving away from a high-carbon energy system that relies on fossil fuels would be difficult for some countries. But the overall view was that the transition to new energy sources would not only help combat climate change but also end the uncomfortable geopolitics of the old energy order. But these hopes were based on illusion. The transition to clean energy would be messy in practice and would bring new conflicts and risks in the short term. By the fall of 2021, amid Europe’s energy crisis, soaring natural gas prices, and surging oil prices, even the most optimistic evangelists of the new energy order realized that the transition would be rocky at best. Any remaining romanticism evaporated when Russia invaded Ukraine in February 2022. The war exposed not only the brutal nature of Russian President Vladimir Putin’s regime and the dangers of over-reliance on aggressive autocracies for energy, but also the risks posed by a fragmented, largely uncoordinated struggle to develop new energy sources and wean the world off old, entrenched ones. One consequence of this confusion is the revival of a concept that seemed anachronistic during the past two decades of explosive growth in energy supplies and utopian visions of a green future: energy security. For many Americans, the phrase conjures up images of the 1970s, conjuring images of boxy sedans and wood-paneled station wagons lined up for miles to fill up with gasoline at the high prices caused by the 1973 Arab oil embargo and the 1979 Iranian revolution. But energy security is hardly a thing of the past: it will be crucial for the future.