Before February 2022, European energy security analysis treated the Persian Gulf as a significant but secondary concern. The primary vulnerabilities ran through Ukrainian pipeline corridors and Russian supply decisions. Hormuz was a risk to Asian energy markets, to oil prices globally, and to a residual flow of LNG from Qatar to a handful of European regasification terminals that had been built for flexibility rather than baseload supply. The invasion of Ukraine changed this with a speed that European energy planners had not fully modeled. By the end of 2022, Europe was competing in global LNG markets for volumes that included substantial Qatari supply, and its exposure to events in the Persian Gulf had become structurally different from anything its policy frameworks had anticipated.

Japan imports approximately 90 percent of its energy. It has no significant domestic fossil fuel production. Its nuclear power sector, which once provided a substantial share of electricity generation, has been operating at sharply reduced capacity since the Fukushima accident of 2011, with only a portion of the pre-accident reactor fleet returned to service. The Gulf supplies the majority of Japan’s crude oil, and Gulf LNG — primarily from Qatar — supplies a substantial portion of its natural gas. There is no combination of alternative energy policies or supply source diversification that changes the fundamental arithmetic on the timescale of months. Japan’s dependence on Hormuz is existential in a way that is not hyperbole.

South Korea is among the most energy-import-dependent economies of any significant size in the world. It has no domestic oil production, minimal natural gas reserves, and a geography that makes pipeline connections to alternative supply sources impossible. Its entire hydrocarbon supply arrives by sea, a majority of it from the Persian Gulf, and all of the Gulf portion transits the Strait of Hormuz. The country has built one of the world’s largest economies and most sophisticated industrial sectors on an energy supply foundation that is concentrated in a single maritime corridor controlled in part by a government that has expressed willingness to disrupt it.

Beneath the shallow waters of the Gulf, shared between Qatar and Iran, lies the North Field — the largest single natural gas reservoir on earth. The Qatari portion is developed. The Iranian portion, called South Pars, is partially developed and severely constrained by sanctions and investment restrictions. What happens to the gas that Qatar extracts from its side of the reservoir determines energy supply conditions for electricity consumers in Japan, industrial gas buyers in South Korea, and power generators across Europe. All of it moves through Hormuz.

Approximately 20 million barrels of oil and petroleum products transit the Strait of Hormuz on an average day. The figure is so large and repeated so frequently in energy commentary that it has become almost abstract. Decomposing it into its constituent flows reveals a more specific picture of what is actually at stake — which countries, which companies, which commodity streams, and which supply chains run through twenty-one miles of contested water.