Iran is making lots of noise about closing the Strait of Hormuz, the vital international waterway that carries 17 million barrels of oil every day—35 percent of the crude oil transported by sea. The control of the Persian Gulf region is in Iran’s hands, Iranian naval chief Habibollah Sayyari ominously warns. This follows news that the Iranian parliament is mulling legislation to block tanker traffic through the strait, which comes on the heels of Sayyari’s boast late last year that closing the strait would be easier than drinking a glass of water. The Iranians have punctuated their threats with missile tests and provocative war games.

Before getting into the West’s response, it’s worth investigating whether Tehran can make good on these threats. The short answer is yes. Tehran is capable of closing the strait—at least temporarily—and thus wreaking havoc with the global economy. As Anthony Cordesman of the Center for Security and International Studies has noted, “Iran has given modernization of its naval forces high priority,” acquiring sophisticated anti-ship missiles from China and Ukraine, submarines from Russia, high-speed attack boats from France and thousands of anti-ship mines. Iran “cannot close the Gulf for an extended period,” according to Cordesman, but it “could severely restrict shipping through the Gulf for five to 10 days”—the time it would take for allied forces to clear away Iran’s mines and neutralize land- and ship-based threats to sea traffic.

Some observers contend that Iran’s rulers would never do such a thing because the consequences would be disastrous for them. In other words, Iran has too much to lose. This line of thinking overlooks two important truths:  First, while it would be wrong to say that Tehran has nothing to lose—after all, in the event of war, Ayatollah Ali Khamenei, Mahmoud Ahmadinejad and their henchmen could lose their regime—it certainly has less to lose today than it did before the West started tightening the sanctions noose. Second, Iran has tried something like this before.

In the mid-1980s, during the Iran-Iraq War, the two belligerents attacked oil tankers transiting the Persian Gulf. When Iran began targeting Kuwaiti tankers, Kuwait proposed sailing its ships under an American flag in hopes of deterring Iranian attacks. Along the way, the U.S. Navy began escorting oil tankers and other ships through the Gulf and Strait of Hormuz. Inevitably, tankers began hitting Iranian mines; commercial ships and aircraft were mistaken for military vessels and warplanes; a U.S. frigate was hit by an errant missile; and an Iranian jetliner veered into the battle space and was shot down.

While most Americans and Canadians forget this war on the Gulf, Tehran doesn’t. It ended with Iran’s naval assets decimated. On a single day in 1988, the U.S. Navy captured an Iranian ship, set Iranian oil platforms ablaze and eliminated six Iranian warships.

For a number of reasons, the West’s goal today should be to keep the strait open while avoiding a shooting war.

First, the global economy is not nearly as robust or resilient as it was in the1980s. A dramatic spike in oil prices triggered by open hostilities in the strait could send already-teetering economies in Europe and North America back into recession.

Second, Iran’s military packs a stronger punch today than in 1988. It can lay between 2,000 and 3,000 anti-ship mines, launch land-based or aircraft-mounted anti-ship missiles, and deploy a fleet of mini-subs that can fire ship-killing torpedoes. Iran also has 100 patrol ships and fast-attack boats that can conduct kamikaze-type missions of the sort that crippled the USS Cole in the Gulf of Aden in 2000. In addition, Iran has a large, lethal and long-range arsenal of ballistic missiles that can strike U.S. and Canadian allies throughout the region and as far away as Europe.

Third, although the U.S. Navy remains a powerful global force, it is being asked to do far more with far less than its 1988 counterpart. At the height of the Reagan buildup, the U.S. Navy boasted 587 ships. The size of today’s fleet is 285 ships and falling. These numbers have real-world implications: Earlier this year, Gen. James Mattis, commander of U.S. Central Command, requested a third aircraft carrier for the Gulf to send a deterrent message after Tehran threatened to attack U.S. ships in the Strait of Hormuz. That request was denied because the extra carrier was needed in the Pacific.

Even so, Washington is committed to keeping at least two carriers in the area for the foreseeable future. In addition, the Pentagon has doubled the number of U.S. minesweepers in the region to eight; rushed dozens of mine-killing drone-submarines to the Gulf; and deployed a squadron of F-22s, America’s most sophisticated fighter-bomber, to the UAE. Last week’s deadly incident involving a speedboat’s erratic approach on a U.S. ship, which ended with U.S. sailors firing on the unresponsive vessel, underscores how serious the U.S. is about keeping the strait and its approaches secure.

But the U.S military is not alone in defending the Strait of Hormuz:

• In September, 20 allied nations will conduct minesweeping drills in the Gulf.
• The HMCS Charlottetown has transited the Strait of Hormuz in recent weeks. HMCS Regina recently deployed to relieve the Charlottetown.
• A number of British naval assets are prowling the Gulf.
• The French carrier Charles de Gaulle is expected to be on station by August. France opened air force and naval installations in Abu Dhabi in 2009.
• The UAE is buying 4,900 JDAM bombs and has opened a new naval base on its coast, intentionally east of the strait.
• The Saudis recently engaged in a $60-billion shopping spree for warplanes, missile defences and bombs.

These buildups, maneuvers and deployments send an important signal to Iran and to global markets—namely, that Iran will not be permitted to hold the global economy hostage by closing the vital sea lanes of the Strait of Hormuz.

It’s a paradoxical truth that such preparations for war in the face of an aggressive enemy like Iran can actually keep the peace. The Romans had a phrase for it: Si vis pacem, para bellum. If you wish for peace, prepare for war. George Washington put it more genteelly: There is nothing so likely to produce peace as to be well prepared to meet an enemy. Churchill called it defence through deterrents, Reagan peace through strength.

It works in two important ways: At its best, it prevents war by deterring the enemy. But even when it fails to deter the enemy—and Iran may be the sort of enemy that cannot be deterred—it equips those nations that truly wish for peace and are prepared to defend it to secure victory rapidly and return to the status quo.