Much of the commentary on the confrontation in the Strait of Hormuz assumes the United States has stumbled into an unprecedented crisis. CNN started the meme claiming unidentified “sources” leaked a classified briefing saying just that, that what was unfolding is racked by confusion and disbelief. The Atlantic followed with a scolding think piece, the NYT with its own version, and then The New Yorker, calling the unpreparedness “inexcusable.” In reality, Washington and Tehran have fought variations of this maritime contest before. What is unfolding today is not Armageddon, just Round Three.

During Trump’s first term Tehran used the same tactics of threatening to block the Strait and attacking oil infrastructure in the Gulf states. In 2018, after pulling out of the Obama nuclear deal, Trump launched a “maximum pressure campaign” against the Islamic Republic, which included extensive sanctions designed to shut down Iran’s oil industry. In February 2019, the Islamic Revolutionary Guard Corps threatened it would close the Strait. It then backed off from full closure, understanding Iran’s need to export oil would likely cripple its society long before global reserves were used up. In early summer 2019, Iran turned up the pressure, sabotaging four oil tankers in the United Arab Emirates. Iranian mines in the Gulf of Oman damaged two freighters, Japanese and Norwegian. A barrel of oil was projected to spike from $65 to as much as $170.

But it didn’t, as Iran backed away from the fight. It could not afford a full blockade of its oil exports to China, which the U.S. could have effected at very low cost, in the Indian Ocean, away from Iranian interference and any closed Strait. Iran also knew while it could harass shipping, it could not seal the Strait to all traffic in the face of the massive U.S. Navy deployment. This was asymmetrical warfare, not peer-on-peer fighting, after all. Iran in 2019 instead chose the long-game: survive sanctions while applying calibrated pressure rather than risking an all-out regime-threatening war. The strategy worked because oil markets react to risk — fear — not necessarily reality. When tensions rise between Iran and the United States, oil prices spike because investors fear shipping could be interrupted. Insurance rates rise over worry about the future, not the present. Threats to the Strait get Iran most of what it needs (survival) at low cost. Temporary chaos can achieve political goals, and makes a helluva diplomatic bargaining chip.

Many of the lessons Iran applied in 2019 were learned in the Iran-Iraq “Tanker War.” Between 1984 and 1988, oil tankers, merchant vessels, and neutral shipping became targets in a campaign designed not to defeat an enemy navy but to strangle an enemy economy. After years of brutal stalemate on land, both Iran and Iraq looked for ways to inflict economic damage on each other. Oil exports were the lifeblood of both states, and nearly all of that oil moved by ship through the narrow waters of the Persian Gulf (the Strait carried a larger share of globally traded oil back then, as compared to 20 percent now). Beginning in 1984, Iraq began attacking tankers carrying Iranian oil. Iran targeted vessels linked to the Arab states, who were mostly supporting Baghdad, and selling to the U.S. Hundreds of ships were attacked, but few were destroyed outright. In total, only 55 of the 239 petroleum tankers (23 percent) struck were completely sunk.

Iran learned its strategy was less about sinking ships than about creating fear of sinking ships. Oil tankers are massive vessels designed to withstand damage. Many ships struck by missiles or mines did not sink but burned before being towed to safety.

But it was the threat that soon drew the United States into the conflict. Kuwait sought protection, and in 1987 Washington agreed to the controversial arrangement of reflagging Kuwaiti tankers under the American flag and having the U.S. Navy escort them. But even the world’s most powerful navy could not fully guarantee safety in such a narrow waterway. The first escorted convoy immediately encountered trouble when the tanker Bridgeton struck an Iranian mine in July 1987. The explosion did not sink the vessel, but it was a public embarrassment. Iran’s tactics exposed the vulnerability of modern shipping. Mines, cheap and difficult to detect and remove, proved effective as tools of harassment. A handful of mines could shut down vast areas of sea.

However, a change in American tactics ultimately neutralized the Iranians. The United States shifted from escorting tankers to directly confronting Iranian forces. The turning point came in April 1988, after a U.S. guided-missile frigate struck a mine in the Gulf. Although the ship survived, the incident triggered a massive American retaliation. American ships and aircraft destroyed Iranian oil platforms used for military surveillance and sank or damaged Iranian naval vessels. SEAL operations destroyed the shore facilities Iran used to launch its mine boats and missiles, and captured Iranian vessels at sea. That the 31st Marine MEU is today steaming toward the Gulf with 2500 special operations capable Marines and its own SEALs suggests the U.S. may be planning to follow a similar strategy.

The operation demonstrated the overwhelming conventional superiority of the U.S. Navy. By the time the Iran–Iraq War ended later in 1988, the Tanker War had produced no victor. Both Iran and Iraq continued exporting oil throughout the conflict. Despite hundreds of attacks, the flow of petroleum through the Gulf never stopped entirely. The maritime campaign could not achieve its strategic objective for Iran, the same lesson learned anew in 2019.

The central lesson is a cautionary one. Military power can keep sea lanes open, but it cannot eliminate fear and risk. The Gulf remains a narrow, congested waterway where accidents, miscalculations, and asymmetric tactics can rapidly escalate if the U.S. allows them to do so. The war reinforced another lesson important today, that protecting commerce at sea may be necessary, but it is never simple, and it is rarely without consequences. America has kicked off a lot here, and it will cost her lives and money to finish it.

So what happens next?