Sustained Tensions in the Strait of Hormuz and Bab el-Mandeb: An Analysis of Risks to South Korea’s Energy and Maritime Security

Executive Summary

The Strait of Hormuz, effectively blockaded since the outbreak of war in February 2026, has entered a new phase following the August 17 expiration of the Islamabad Memorandum. Iran's unilateral transit system is now solidifying as the de facto standard route, despite lacking a legal basis. The blacklisting of 45 vessels, including a tanker owned by Sinokor Merchant Marine, by Iran's Persian Gulf Strait Authority is the first demonstration that this system has real enforcement power. The United States has sanctioned over 60 entities under "Operation Economic Outcast" but has opted for selective enforcement by excluding major Chinese banks. South Korea is expected to face a similar package of demands, calling for both participation in sanctions and a military contribution. Over the next six months, the most likely scenario (50% probability) involves alternating periods of negotiation and tension, with Brent crude expected to fluctuate within a $88–$95 per barrel range. The South Korean government and companies must adopt a dual-track approach: decoupling their response to U.S. demands for sanctions participation from negotiations with Iran to remove vessels from the blacklist. This should be complemented by diversifying supply sources and maintaining an early warning system by monitoring the Omani mediation channel.

I. Situational Analysis

Situational Analysis: Tensions in the Strait of Hormuz and Bab el-Mandeb and Asian Energy Security

1. Background and Developments

The current crisis began on February 28, 2026, when U.S. and Israeli airstrikes on targets inside Iran triggered a full-scale war in the Middle East [8][12]. Since the war's outbreak, the Strait of Hormuz has been under a de facto blockade [8][12]. Before the conflict, the strait was a critical route for approximately one-fifth of the world's crude oil and LNG supplies [8][12][15].

On June 17, President Trump and the Tehran government signed a memorandum of understanding known as the "Islamabad Memorandum" [6][12]. It called for an immediate and permanent cessation of military actions on all fronts [6][10]. Immediately after signing, President Trump declared a resumption of normal navigation, stating, "Ships of the world, start your engines" [12]. However, the memorandum expired on August 17 [10][12].

Following the memorandum's expiration, Iran shifted from a defensive to an offensive posture [10]. The Iranian Foreign Ministry condemned the announcement of new U.S. sanctions as an "extraterritorial exercise of sovereignty over all UN member states" [11]. The fact that all 11 vessels transiting the Strait of Hormuz as of August 11 used Iran's unilateral transit system demonstrates that this system has become the de facto standard route, despite lacking a legal basis [12].

2. Current Situation

The situation entered a new phase around August 23–24. On August 24, the United States announced new sanctions against Iran, dubbed "Operation Economic Outcast," sparking speculation that China, Iran's largest trading partner, could also be affected [7][11][14]. Iran's Foreign Ministry again denounced the move as a violation of sovereignty and signaled a firm response [11][13]. Reports from Cairo and Washington indicate that the two sides have been in a six-month stalemate, "exchanging no fire but pursuing no peace talks" [7][11][13][14].

Amid this situation, on August 23, Iran's Persian Gulf Strait Authority announced it had blacklisted 45 vessels for violating transit rules, including a tanker owned by South Korea's Sinokor Merchant Marine [1]. The authority stated that blacklisted vessels could face fines, detention, and cargo seizure [1]. This case demonstrates that Iran is using its self-declared unilateral transit system as a real enforcement tool.

Traffic through the Strait of Hormuz has shown a marked decline in recent days. According to data from the maritime tracking firm Kpler, the number of transiting vessels has failed to rebound since August 20 [16]. The UAE-based newspaper *The National* reported that China's imports of Iranian crude have fallen by 48% since the war began, and that Chinese state-owned shipping companies like COSCO Shipping and China Merchants Energy Shipping have voluntarily suspended routes through both the Strait of Hormuz and the Bab el-Mandeb Strait since July [17]. The newspaper also reported that while the U.S. Treasury Department designated over 60 entities for sanctions, it has refrained from directly sanctioning major Chinese banks [17].

Japan is pursuing a separate diplomatic track. Foreign Minister Toshimitsu Motegi has completed a tour of Saudi Arabia and Oman, while Prime Minister Sanae Takaichi is making direct calls to regional leaders to request their help in securing navigational safety [4]. The Thai newspaper *The Nation* analyzes that these moves stem from Japan's structural vulnerability, as it depends on the Middle East for 90% of its crude oil imports [4]. During his six-day Gulf tour, Foreign Minister Motegi focused his discussions with his counterparts on the security of the two straits [4].

3. Key Actors and Interests

Iranseeks to gain negotiating leverage by establishing and enforcing its own transit rules through the Persian Gulf Strait Authority [1][10]. The coordinated hardline messaging from Iran's Foreign Ministry, Supreme National Security Council, and Revolutionary Guard Corps since the Islamabad Memorandum's expiration suggests that Iran, having survived attempts at regime collapse, has shifted from a defensive to an offensive posture [10]. Iran maintains its position that it will use force to block the passage of unauthorized tankers [7][13].

United Statesis seeking an off-ramp through economic warfare after failing to achieve its initial goals of regime change and the dismantlement of nuclear facilities [8][10]. As Vice President Vance has indicated, Washington's priority has shifted to stabilizing domestic consumer oil prices, signifying a departure from its past practice of providing the public good of protecting Gulf sea lanes for free [8]. The new sanctions target China, Iran's largest trading partner, but the U.S. has opted for selective enforcement by excluding major Chinese banks from the designations [7][11][17].

Chinahas little incentive to join the sanctions, as it imports over 80% of Iran's crude oil [2]. Nevertheless, its imports have dropped by 48% since the war began, and its state-owned shipping companies are showing a dualistic attitude by voluntarily avoiding the high-risk routes [17]. This can be interpreted as a characteristically Chinese approach of separating political support from practical risk management.

Japanis leveraging its position as a non-party to the conflict to focus on diplomatic mediation and establishing channels to ensure safety [4]. The diplomatic tour by Foreign Minister Motegi and direct calls by Prime Minister Takaichi are preemptive responses to the country's structural vulnerability, with 90% of its crude oil sourced from the Middle East. Notably, Japan has chosen to diversify its diplomatic channels rather than pursue military intervention [4].

South Koreahas been drawn into the conflict as a direct party after a tanker owned by Sinokor Merchant Marine was placed on Iran's blacklist [1]. This incident shows that South Korea is not a mere bystander in the U.S.-Iran conflict but is directly exposed to its risks.

International Maritime Organization (IMO)has stated that it is monitoring the safety of over 20,000 seafarers in the region, including those on vessels stranded in the Strait of Hormuz [3]. This indicates that the risks in the strait are expanding from commercial shipping operations to issues of human safety.

4. Key Issues

The first issue is the legal status of Iran's unilateral transit system. While this system has become the de facto standard route, its basis in international law is unclear [2][12]. The Stockholm International Peace Research Institute (SIPRI) points out that the wording of the Islamabad Memorandum implies the U.S. might accept Iran's restrictions on navigation as part of a final peace agreement. SIPRI warns that such a development could have repercussions for the principle of freedom of navigation worldwide, extending beyond the Gulf region [6].

The second issue is the potential for the U.S. to link demands for sanctions participation with calls for security contributions. There is speculation that the United States may present its allies with a single package demanding both participation in anti-Iran sanctions and military contributions in the Strait of Hormuz [10]. Asian trading nations, including South Korea, face the challenge of needing to respond to these two demands separately [8][10].

The third issue is the viability of the Omani mediation channel. President Trump's threatening remarks regarding Oman are destabilizing what has been virtually the only functioning mediation channel in the Gulf region. This is seen as a variable that could dismantle the existing dynamic of alternating negotiation and tension [12].

The fourth issue is the duration of pressure from high oil prices and logistics costs. Brent crude is fluctuating within an $88–$95 per barrel range [5][8]. The fact that the performance recovery of Southeast Asian low-cost carriers is being delayed by the impact of rising oil prices shows that this pressure is spreading throughout the aviation and shipping industries of energy-importing countries.

II. In-Depth Analysis

In-Depth Analysis: The Structural Roots and Key Variables of the Hormuz and Bab el-Mandeb Blockade

1. Root Cause: Design Flaws in the Memorandum Framework

The Islamabad Memorandum was a compromise between the military setback of a failed regime change attempt and the economic goal of maintaining low oil prices [8][12]. The Trump administration tried for six months to collapse the Iranian regime but failed to achieve its objective [10]. Even though Supreme Leader Khamenei was killed in an Israeli airstrike, the Iranian regime itself survived [10]. This failure was the decisive factor that shifted U.S. policy priorities.

The shift in policy priorities, as articulated by Vice President Vance, directly reflects this structure. The goal of U.S. policy toward Iran moved from "regime change and dismantlement of nuclear facilities to stabilizing consumer oil prices" [8]. Unable to topple the regime, Washington's next-best option was to manage oil prices, and the Islamabad Memorandum was the product of that alternative strategy. The problem was that the memorandum only declared an end to the war; it did not explicitly include an agreement on the method of transit through the Strait of Hormuz. SIPRI notes that the wording of the memorandum's key provisions leaves open the "possibility that the United States might permanently permit Iran's restrictions on freedom of navigation in the Strait of Hormuz as part of a final peace agreement" [6]. The war ended, but the legal status of freedom of navigation was left unresolved as the August 17 expiration date approached.

Underlying this design flaw is a shift in America's structural interests. Thanks to the shale revolution, the United States has more than quadrupled its oil production since 2008, transforming from a net importer to a net exporter [8]. Protecting the Gulf sea lanes was once a public good that the U.S. provided free of charge to its allies. However, as the country no longer relies on these routes, the political incentive to provide this public good has diminished [8]. This change stems not from President Trump's personal negotiating style but from the structural transformation of the U.S. energy industry, making it a trend that is difficult to reverse even with a change in administration [8].

2. Structural Context: A Three-Tiered Power Struggle

At the political level, Iran's domestic power centers are simultaneously issuing hardline messages. The Foreign Ministry, the Supreme National Security Council, and the Revolutionary Guard Corps are all sending offensive signals through their respective channels [10]. This circumstantial evidence supports the assessment that Iran has shifted from a defensive to an offensive posture since the memorandum's expiration [10]. The blacklisting of 45 vessels, including a South Korean ship, by the Persian Gulf Strait Authority represents the implementation phase of this offensive shift [1].

At the economic level, China's role is decisive. China is the largest customer for Iranian crude, accounting for over 80% of its imports [2]. The new U.S. sanctions announced on August 24 targeted over 60 entities but excluded major Chinese banks from direct designation [17]. This shows that Washington is pursuing a selective enforcement strategy, sending a pressure signal to Iran while avoiding a full-blown confrontation with China. Nevertheless, China's imports of Iranian crude have already fallen by 48% since the war began, and state-owned shipping companies like COSCO Shipping and China Merchants Energy Shipping have voluntarily suspended operations on the Hormuz and Bab el-Mandeb routes since July [17]. In effect, market participants are already engaging in self-censoring avoidance behavior even before the explicit enforcement of sanctions.

At the security level, Oman's status as a mediator serves as the sole buffer supporting this entire structure [10][12]. President Trump's remarks suggesting the possibility of bombing Oman are seen as a variable that could destabilize this buffer itself [12]. If the Oman channel collapses, the current cyclical structure of alternating negotiation and tension will cease to exist.

3. Historical Precedent: Comparison with the Tanker War and Key Differences

The "Tanker War" during the 1980s Iran-Iraq War is often cited as the archetype of threats to transit in the Strait of Hormuz. At that time, Iran also threatened vessels in the Gulf, and the United States responded by dispatching its fleet to escort merchant ships. The fundamental difference from the current situation lies in the U.S. will to intervene. In the 1980s, the U.S., as a net oil importer, had a direct interest in maintaining freedom of navigation in the Gulf. Today, having become a net exporter, the urgency of that interest has diminished [8]. This context explains why the current U.S. administration relies on the indirect means of economic sanctions rather than military escorts.

The 2019 Hormuz crisis also serves as a reference point. Although threats of tanker seizures and detentions were repeated then, the situation de-escalated within a few months, and the principle of freedom of navigation was not fundamentally altered. The current situation is structurally more serious because Iran's self-designed unilateral transit system has in fact "become the standard route" [2][12]. The fact that all 11 vessels transiting on August 11 used this system means that a management regime with no basis in international law has solidified into the de facto standard for the route [12]. Whereas the 2019 crisis was a temporary friction, the current situation is a qualitatively different phase, as a reorganization of the navigational order itself is underway.

4. Key Variables: The Oman Channel and the Scope of Sanctions Enforcement

The first variable that will shape future developments is the survival of the Omani mediation channel. EAI assesses that this needs to be monitored as a "separate early warning indicator" [10][12]. As long as this channel remains open, the pattern of alternating negotiation and tension within a contained range is likely to continue. However, its collapse could trigger a rapid shift toward a more pessimistic trajectory.

The second variable is the scope of U.S. sanctions enforcement. The August 24 measure, which excluded major Chinese banks from sanctions, suggests that Washington is opting for a selective and phased enforcement approach [17]. However, it is uncertain how long this selectivity will last. If sanctions are extended to China's payment networks, the current blockade could lead to a much more drastic realignment of logistics.

The third variable is whether the U.S. presents its demands for security contributions and sanctions participation as a single package [8][10]. If the two demands are combined, Asian countries, including South Korea, will be pressured to make a comprehensive choice rather than responding to each issue individually. EAI has repeatedly pointed out that decoupling these two issues must be the central pillar of any response strategy [8][10].