There are advantages to such an acquisition. Nuclear propulsion grants SSNs virtually boundless seakeeping ability, letting them prowl their patrol grounds for months at a time. Long on-station times explain SSNs’ allure with Brazilian navalists. However, it remains unclear precisely what they expect a nuclear-attack boat to do after detecting unlawful fishing, drilling, or undersea mining. If patrol craft are constables who tote nightsticks, then SSNs are infantrymen who brandish battle-axes meant to split skulls.

Clobbering a fishing boat with torpedoes and anti-ship missiles, typical submarine armament, would amount to overkill—and pricey overkill at that.

Bottom line, Brazil’s navy craves ships normally meant for conventional naval warfare—but it craves them for eccentric reasons. In one sense the Marinha resembles the U.S. Navy after World War I, which is when imperial Germany had been vanquished but no competitor had yet taken its place as the focal point of U.S. naval strategy. In 1919 Captain Harry Yarnell quipped that trying to design a fleet with no enemy in sight is like forging a machine tool without knowing whether its users intend to manufacture hairpins or locomotives.

In other words, strategic drift prevails when a service has no foe to impart direction to force design and operations. But there is an upside to Brazilians’ offbeat fascination with high-end carriers and subs: if the navy ever needs a concept of war, then some of the platforms needed to put a warlike concept into practice will already reside in the inventory. The navy can and should experiment with them, honing battle doctrine and skill lest more forbidding times come.

As they may. Perpetual peace has not come to the South Atlantic any more than it came to Europe under U.S. military protection. In reality Brazil is enjoying a holiday from history courtesy of the U.S. Navy—a silent partner in its maritime defense.

And there’s justice to that: the United States free-rode on maritime security furnished by Great Britain’s Royal Navy for most of the nineteenth century, and benefited immensely from the respite from great-power rivalry. The republic was able to subdue a continent, fight its civil war, and foster an industrial revolution precisely because British naval mastery staved off predatory empires—sparing Washington from fielding a pricey navy or army to defend its shores and interests.

Resources that might have gone into a large standing military went to economic development, or stayed in private hands. Industry flourished.

But the lesson of the nineteenth-century United States for twenty-first-century Brazil is this: holidays don’t last forever. Use them well.

British maritime supremacy came under duress toward the nineteenth century’s end. The advent of new industrial powers—Germany, Japan, the United States—cut into Britain’s material advantage. And when one of those competitors, imperial Germany, decided to construct a great battle fleet hard by the British Isles, the leadership in London felt compelled to being warships home from the Far East and Western Hemisphere.

The Americas’ external protector started withdrawing. American republics had to provide for their own defense, or go undefended.

Starting in the 1880s, happily, the United States had laid the keels for its first steam-propelled, armored, big-gun fleet. The U.S. Navy took up the burden of maritime security as the Royal Navy drew down its American Station and went home to run its arms race against Germany. By the dawn of the twentieth century Washington had built up a surplus of naval might that enabled it to guarantee nautical freedom in the Western Hemisphere.

It could do all this because London had given it a holiday from history.

But the surplus of U.S. sea power could prove perishable, like all things. China’s rise, Russian troublemaking, and sundry Eurasian challenges now beckon U.S. attention, policy energy, and martial resources to distant waters and shores. Whereas German sea power pulled the Royal Navy home, great-power mischief-making siphons U.S. naval power away from home. Eurasian adventures could expose the Americas to fresh dangers in their naval protector’s absence.

So, Brazil, by all means experiment with aircraft carriers and nuclear-powered subs. You may need them—along with a concept of how to use them in combat. Hemispheric defense could use a joint custodian under all circumstances, not just congenial ones.

Enjoy Venus—but spend some time on Mars.

James Holmes is J. C. Wylie Chair of Maritime Strategy at the Naval War College and coauthor of Red Star over the Pacific (second edition published October 2018). The views voiced here are his alone. This piece was originally featured in May 2018 and is being republished due to reader's interest.

Image: Reuters