US Navy Warships Sail Through Strait of Hormuz to Clear Mines and Open Shipping Route

On the morning of April 11, 2026, the guided-missile destroyers USS Frank E. Peterson and USS Michael Murphy crossed the Strait of Hormuz into the Arabian Gulf — the first U.S. warships to transit the waterway since the United States and Israel began bombing Iran on February 28 [1][2]. U.S. Central Command said the ships were operating "as part of a broader mission to ensure the strait is fully clear of sea mines previously laid by Iran's Islamic Revolutionary Guards Corps" [2]. Within hours, Iran denied the crossing had occurred, and the IRGC vowed "a strong response" to any military vessels passing through [2].

The operation sits at the intersection of a six-week-old war, a fragile ceasefire, the first direct U.S.-Iran diplomatic engagement since the 1979 revolution, and the largest disruption to global energy markets since the 1973 oil embargo. What follows is an examination of what is known about the mines, the legal and military realities of clearing them, and the economic and geopolitical consequences that flow from the 21-mile-wide chokepoint that the world's energy supply depends on.

The Mines: What's in the Water

U.S. officials have identified at least a dozen underwater mines in the strait based on intelligence assessments [3]. CBS News reported that two specific Iranian-manufactured devices have been documented: the Maham 3, a moored mine that uses sensors to detect passing targets, and the Maham 7, a bottom-resting "sticking mine" triggered by the magnetic or pressure signatures of vessels passing overhead [3].

These represent two of the three principal categories of naval mines. Moored mines like the Maham 3 are tethered to the seabed and float at a set depth; bottom mines like the Maham 7 sit on the seafloor and are harder to detect with conventional sonar because they blend into the terrain. A third category — drifting mines — may also be present. According to the New York Times, as reported by the Jerusalem Post, Iranian forces "did not systematically track every placement and, in some cases, deployed mines in ways that allowed them to drift from their original positions" [4]. Iranian authorities now reportedly cannot reliably map, locate, or recover all of the weapons they deployed [4].

The total number of mines remains uncertain. During the 1987–1988 Tanker War, Iran deposited approximately 150 mines in the strait [5]. The current extent of mining is smaller by most estimates, but the Stimson Center notes that Iran's approach treats "cheap, asymmetric weapons" as "strategic leverage against the U.S. Navy" — a doctrine in which "a few mines or the threat of mining would be just as effective as a blockade" [6].

A Navy Stretched Thin

The mine-clearing mission exposes a long-standing gap in U.S. naval readiness. Mine countermeasures funding accounts for "less than 1% of the Navy's total budget," according to maritime security expert Scott C. Truver, who described the field as a "stepchild of the U.S. Navy" [7].

Emma Salisbury of the Foreign Policy Research Institute said she was "honestly completely baffled" that mine-clearing resources were not positioned in the Middle East when the conflict began. "Having a mine countermeasures capability that is not in theater is not particularly helpful," she told NPR [7]. The Navy's dedicated mine countermeasures vessels — the USS Santa Barbara, USS Tulsa, and USS Canberra — were stationed in Singapore or elsewhere in Asia at the time of the transit [7].

The Navy is in the process of replacing older Avenger-class minesweepers, in service since the 1980s, with Independence-class Littoral Combat Ships equipped with Mine Countermeasures (MCM) mission packages that integrate unmanned vehicles, MH-60S helicopters, and sonar systems. But a March Pentagon report found that "no operational testing" of the Independence-variant LCS with MCM packages had occurred in fiscal 2025, and that "operational effectiveness…cannot be determined…due to insufficient performance data" [7].

CENTCOM stated that additional forces, including underwater drones, will join the clearance effort in the coming days [2]. Historically, the United States has relied on European NATO allies for mine-clearing support. Poland maintains over two dozen mine-clearing ships, and the U.K., France, and Turkey also operate substantial fleets [7]. Whether allied assets will be deployed to the Gulf remains unclear.

The Legal Terrain

The Strait of Hormuz qualifies as an international strait under Article 37 of the UN Convention on the Law of the Sea (UNCLOS), which guarantees that "all ships and aircraft have a right of transit passage, which shall not be impeded" [8]. UNCLOS Article 44 further stipulates that "there shall be no suspension of transit passage" [8].

Neither the United States nor Iran has ratified UNCLOS. Iran signed the convention but has argued that its transit passage provisions were "quid pro quo" bargains rather than binding customary law, and enacted a 1993 domestic law allowing suspension of foreign vessel passage and requiring authorization for ships carrying "dangerous or harmful materials" — a category that could encompass oil tankers [9].

The United States takes the opposite position: its Freedom of Navigation program treats transit passage as customary international law binding on all states regardless of UNCLOS ratification [9]. The 1949 Corfu Channel case at the International Court of Justice, in which Albania was held responsible for mine damage to British warships in international straits, is frequently cited as precedent [9].

The gap in existing legal frameworks is significant. As the Lawfare Institute observed, the current rules governing naval warfare were "developed during geographically-limited conflicts, not modern chokepoint disruptions affecting dozens of neutral economies simultaneously" [9]. The mine-clearing operation tests whether transit passage rights extend to the active removal of weapons from waters that both Iran and Oman claim as territorial seas.

The Economic Shock: By the Numbers

Before the conflict, approximately 20 million barrels per day of crude oil and petroleum products — about 20% of total world petroleum liquids consumption — moved through the Strait of Hormuz [10][11]. That included roughly 15 million barrels per day of crude oil and condensate and 5.5 million barrels per day of refined products [10]. The strait also carried approximately 20% of the world's liquefied natural gas [11].

On March 2, 2026, a senior IRGC official confirmed the strait was closed and threatened any ship that passed through [11]. Tanker traffic dropped by about 70% within days and soon fell to near zero [11].

Source: FRED / EIA

Data as of Apr 6, 2026CSV

WTI crude oil stood at $114.01 per barrel as of early April 2026, up 86.7% year over year [12]. The Dallas Federal Reserve modeled multiple scenarios for the closure, finding that a one-quarter disruption would push WTI to $98/barrel, while a two-quarter closure would peak at $115/barrel and a three-quarter closure would reach $132/barrel [13]. The Dallas Fed characterized this disruption as "three to five times larger" than past geopolitical oil crises — the 1973 and 1990 disruptions removed about 6% of supply, and the 1979–1980 crisis about 4%, compared to 20% in the current episode [13].

The annualized GDP impact is severe: the Dallas Fed estimated a 2.9 percentage-point reduction in quarterly real GDP growth during the closure, with full-year effects ranging from -0.2 to -1.3 percentage points depending on duration [13].

Who Is Exposed: Asia's Import Dependence

The countries most dependent on Hormuz flows are concentrated in Asia. In 2024, China received 5.7 million barrels per day through the strait, followed by India at 2.2 million, South Korea at 1.8 million, and Japan at 1.6 million [10][14]. Together, these four nations accounted for 69% of all crude oil and condensate flows through the strait [14].

Source: EIA / Visual Capitalist

Data as of Mar 1, 2026CSV

Their strategic reserves vary widely. South Korea holds strategic petroleum reserves equivalent to roughly 200 days of supply [14]. China's strategic petroleum reserve is estimated at approximately four months' coverage [14]. For LNG — on which Japan and South Korea are particularly dependent — reserves are far thinner: South Korea holds about 3.5 million tons and Japan about 4.4 million tons, enough for roughly two to four weeks of stable demand [15].

Japan faces the most direct risk due to its high share of oil and gas trade through the strait and near-total reliance on imported energy, with South Korea ranked second, India third, and China fourth [14]. The Christian Science Monitor reported that several Asian governments have implemented belt-tightening measures, including fuel rationing and conservation mandates [16].

Insurance, Rerouting, and Second-Order Costs

The financial ripple effects extend well beyond crude prices. Before the conflict, war-risk insurance premiums for Hormuz transit ran 0.15% to 0.25% of hull value per one-week policy. Since fighting began, quotes have reached 5% to 10% of hull value — a surge of more than 300% compared to January 2025 levels [17]. Several major shipping lines have imposed war risk surcharges of $500 to $1,500 per container (TEU) [17].

With both the Strait of Hormuz and the Red Sea effectively closed — Houthi-controlled Yemen resumed attacks on commercial shipping on February 28 [11] — tankers and container ships have been forced around Africa's Cape of Good Hope. This adds 16 to 32 days of transit time for tankers on the Asia-to-Europe route and approximately $933,000 in additional fuel costs per voyage for an Aframax-class tanker [18]. Overall fuel consumption rises by nearly 40% [18].

Spot container rates on major routes have climbed approximately 150% since late February. Asia-to-U.S. West Coast rates, previously running $1,800–$2,200 per 40-foot container, surged above $4,500 [18]. Henning Gloystein of the Eurasia Group warned that even after the strait reopens, shipping companies would need at least two months to resume normal operations, with infrastructure repairs necessary [3].

1988 vs. 2026: The Tanker War Comparison

The closest historical precedent is the 1987–1988 phase of the Iran-Iraq Tanker War, when Iran laid approximately 150 mines in the strait, one of which nearly sank the USS Samuel B. Roberts in April 1988 [5]. During the broader Tanker War (1981–1988), more than 450 merchant ships were targeted, with Iraq responsible for 283 attacks and Iran for 168 [5].

The 2026 crisis differs in several respects. Approximately 15 vessels have been attacked since February 28, 2026, with Iran using a layered approach combining shore-launched anti-ship cruise missiles, unmanned aerial vehicles, and explosive unmanned surface vessels in addition to mines [5]. The mining itself appears less extensive than 1988 — "at least a dozen" mines versus 150 — but the economic impact is more severe because of structural changes in global energy markets.

In 1988, the Persian Gulf produced about 20% of global oil; today, the proportion flowing through Hormuz is similar, but the global economy is more tightly integrated, spot pricing transmits disruptions faster, and LNG — which barely existed as a traded commodity in 1988 — now flows through the strait at globally significant volumes. The Dallas Fed notes that the 2026 disruption removes three to five times more supply than any previous geopolitical oil shock [13].

One offsetting factor: strategic petroleum reserves are larger today. The IEA member countries collectively hold roughly 4.1 billion barrels of emergency oil stocks [10]. The 1988 Tanker War never triggered a coordinated reserve release; whether the current crisis will remains an open question.

The Escalation Debate

The strongest case that the mine-clearing operation stabilizes the situation rests on economics: roughly $1 billion in goods transits the strait daily [10], and every day of closure inflicts compounding damage on dozens of economies. President Trump framed the operation as "a favor to Countries all over the world, including China, Japan, South Korea, France, Germany, and many others" [3]. Admiral Brad Cooper said the goal was to "establish a new passage" and "share this safe pathway with the maritime industry soon to encourage the free flow of commerce" [2].

The case that it escalates is advanced by several analysts. Maria Sultan, director general of Pakistan's South Asian Strategic Stability Institute, argued that free U.S. movement through the strait would require Tehran's permission, making unilateral transit "impossible" without provoking a response [2]. Iran called the crossing a ceasefire violation and the IRGC's Revolutionary Guards Navy Command stated that "any attempt by military vessels to pass through the Strait of Hormuz will be dealt with severely" [2][3].

The timing compounds the concern. The mine-clearing transit occurred the same day Vice President JD Vance was in Islamabad for trilateral talks with Iran and Pakistan — the first direct U.S.-Iran face-to-face engagement since the 1979 Islamic Revolution [2][3]. The talks reportedly dragged past eight hours, with control of the Strait of Hormuz among the main points of "serious disagreement" [19]. Critics contend that a unilateral military operation in disputed waters, conducted during active negotiations, narrows the space for diplomatic concessions.

Trump, for his part, dismissed the negotiations' importance: "Whether we make a deal or not, makes no difference to me, because we've won" [2]. Iran's position remains that the strait is under its sovereign control and that passage requires its authorization — a stance at direct odds with U.S. freedom of navigation doctrine.

What Comes Next

The mine-clearing operation is expected to take weeks at minimum, with CENTCOM planning to deploy underwater drones alongside the two destroyers [2]. The untested status of the Navy's newest mine countermeasures systems raises questions about the timeline. Salisbury's concern is not whether the equipment works once, but whether it can perform "over and over at the tempo that would be needed" [7].

The economic consequences are already locked in for the 30-to-90-day window regardless of how quickly the strait reopens. Insurance underwriters will not immediately reduce war-risk premiums. Rerouted tankers and container ships cannot be recalled mid-voyage. Fuel price increases in import-dependent economies — particularly in South and East Asia — will continue to propagate through supply chains.

The central question is whether the mine-clearing operation accelerates the return to open commerce or triggers the next phase of escalation between two adversaries communicating simultaneously through warships and diplomats. The answer depends in large part on whether Iran treats the transit as a ceasefire violation warranting military response, or as a fait accompli it cannot reverse. As of April 12, both possibilities remain open.