Originally written on 4/30/2024

In his recent book, The Neptune Factor, Nicholas Lambert argues that Captain Alfred Thayer Mahan’s concept of Sea Power has generally been misunderstood. Most think Mahan’s point is about combat and military prowess, but it is really about the economic implications of naval power. International oceanic trade has historically been essential for national wealth and power. Lambert suggests this is crucial in understanding how rivalries at sea shaped human history.  

In 1609, Hugo Grotius published his pamphlet Mare Liberum, which translates as Freedom of the Seas. At the time, the Portuguese claimed they had a monopoly right to trade with southeast Asia and closed the oceans to the Dutch and other countries. Grotius argued that every country had the right to trade with every other country. Even landlocked countries should have access to the seas. The sea was common property to everyone, which is a foundation of international law.  

Mahon wrote in the late 1800s and early 1900s during the first period of globalization and viewed access to the ocean commons as crucial to a global economy. Mahan noticed that national economies depended on uninterrupted access to global trading networks. Any nation or empire’s political staility and economic growth depended crucially on access to the ocean commons. This dependence raised the significance of naval prowess and sea power. 

A nation’s sea power was essential to safeguard its own and its allies’ trade. It could also be used to deny access to its enemies and competitors. Nazi Germany used its submarines in World War 2 to try to blockade, destroy, and literally starve England’s economy and citizens.  

Much like today, Mahon wrote during a period of rapid technological and social change. It was a time when sailing ships became obsolete. Propulsion and ship design technologies were rapidly changing. It was a time when Britain, the naval superpower, was facing new competitors. Naval power depended on a strong economy, and a strong economy depended on access to trade networks.  

Recently, conflicts about freedom of the seas have occurred in the Persian Gulf as Houthi rebels attacked shipping, causing many ships to take long voyages around Africa, inflating oil prices and generally raising costs. We see battles for control of shipping out of Ukraine, access to the South China Sea, piracy off the coast of Somalia as today’s manifestation of the importance of sea power. It mattered in the 17th century and will matter in the 22nd.