Maritime Defense Weekly: Enforcement Tightens Across Global Shipping

The Week in Focus

• Sanctions enforcement shifted toward operational constraint, as the EU introduced a full maritime services ban for Russian crude oil and sanctioned 43 additional shadow fleet tankers, while the U.S. expanded sanctions on Iran-linked oil trade, increasing exposure for insurers and service providers.
• Iran escalated in the Gulf without closing routes, seizing two oil tankers near Farsi Island and threatening a U.S.-flagged vessel, continuing a pattern of pressure through seizures rather than blockade.
• India conducted rare high-seas interdictions, boarding three U.S.-sanctioned, Iran-linked shadow fleet tankers in the Arabian Sea following surveillance-led analysis.
• A container vessel casualty off Phuket highlighted non-sanctions risk, as the Panama-flagged Sealloyd Arc sank after a sudden list, triggering salvage and environmental response.
• Western Hemisphere energy pressure intensified without interdiction, as U.S. secondary tariffs on Cuban oil were followed within days by Mexico halting shipments, reshaping maritime flows.
• Behavioral risk surfaced in Northeast Asia, where Windward detected a 429% increase in DPRK-risk vessels drifting inside Japan’s EEZ following North Korean missile tests, including coordinated tandem movement.

Maritime Enforcement Is Shifting From Designation to Constraint

Maritime enforcement is increasingly focused on restricting how vessels operate in practice, not just on whether they appear on a sanctions list. Rather than relying solely on designations, recent actions are targeting the services and access that make maritime trade possible, including insurance, financing, port entry, and maritime support services.

This shift is visible in parallel U.S. and EU moves this week. The European Union announced measures that effectively undercut the price cap framework by imposing a full maritime services ban for Russian crude oil and sanctioning 43 additional shadow fleet tankers, expanding pressure beyond cargo ownership to the insurers, service providers, and intermediaries that enable maritime trade. In parallel, the United States imposed new sanctions on Iranian oil-linked vessels and firms, reinforcing the same approach.

Taken together, these actions apply pressure at the operational layer of shipping. Vessels may still be seaworthy, but their ability to insure, charter, service, or trade legally is increasingly constrained, transferring risk from sanctioned entities to shipping companies, insurers, and service providers that enable movement at sea.

Tactical Escalation in the Gulf Without Route Closure 

Iran escalated tactically this week by seizing two oil tankers near Farsi Island in the Gulf. According to the IRGC-linked Tasnim news agency, the vessels were accused of smuggling over one million liters of fuel, and 15 foreign crew members were referred to the judiciary. The flags of the vessels were not disclosed.

🚨🇮🇷BREAKING :Iran’s Islamic Revolutionary Guard Corps says it has seized two oil tankers in the Persian Gulf, alleging they were carrying around one million liters of smuggled fuel. About 15 foreign crew members were reportedly on board. pic.twitter.com/U0r6v1TkxC

— Defense Intelligence (@DI313_) February 5, 2026

The seizures occurred amid heightened tension, following U.S. naval deployments to the region and renewed warnings from Washington over Iran’s nuclear posture. Iranian authorities said that the vessels had been under surveillance for months, framing the action as a law enforcement rather than a military escalation.

This pattern is familiar. Iran has repeatedly targeted tankers it claims are involved in illicit fuel trade, particularly in the Gulf and Strait of Hormuz, using seizures to apply pressure without declaring closure or blockade. In a recent incident, IRGC fast boats also approached and threatened a U.S.-flagged tanker in the Strait of Hormuz before the vessel increased speed and maneuvered away under naval escort.

This signals controlled escalation – seizures increase risk and insurance exposure without crossing thresholds that would force a broader military response or disrupt traffic at scale.

Indian Coast Guard Boards Three Iran-Linked Tankers on the High Seas

On Friday, the Indian Coast Guard interdicted three Iran-linked shadow fleet tankers in the Arabian Sea following surveillance and data-led analysis. The vessels were boarded roughly 100 nautical miles west of Mumbai, outside Indian territorial waters, marking a rare high-seas enforcement action by a regional maritime power.

The ships – Al Jafzia (IMO 9171498), Asphalt Star (IMO 9463528), and Stellar Ruby (IMO 9555199) – are all under U.S. Treasury sanctions for involvement in Iran’s oil trade. Investigators reported coordinated voyage patterns and ship-to-ship activity linking Iranian transfer zones near Basrah and Khor Fakkan with India’s west coast, in a context where widespread AIS spoofing is used across the Iranian oil trade to mask such movements. Electronic data and crew interrogation revealed indicators of a broader handler network, and open-source reporting links the three tankers to a sanctioned shipowner, Jugwinder Singh Brar, whose fleet has been used to move Iranian petroleum.

Container Vessel Sinks Off Phuket After Sudden Listing 

A Panama-flagged container vessel, Sealloyd Arc, sank off Phuket over the weekend after developing a sudden and severe list while en route from Port Klang to Chattogram. The master issued an abandon-ship call on Saturday afternoon, and all 16 crew members were evacuated safely by Thai authorities within an hour.

The vessel, reportedly carrying around 200 containers, sank the following day. Aerial surveys indicated a small oil spill, prompting Thai maritime authorities to establish a command center to oversee salvage operations, container tracking, and environmental monitoring. An accident investigation is ongoing.

Western Hemisphere Energy Pressure Without Interdiction

Energy enforcement pressure continues to intensify in the Western Hemisphere without the use of physical blockades. President Trump’s executive order authorizing secondary tariffs on oil sales to Cuba was followed within days by Mexico halting oil shipments to Cuba, illustrating how discretionary economic tools can quickly reshape maritime flows.

This approach follows the same pressure model applied to Venezuelan and Russian oil. Rather than targeting vessels at sea, enforcement is applied upstream and downstream through trade access, tariffs, and service exposure. The result is flow disruption without interdiction, limiting escalation while preserving leverage.

Developments in Venezuela further reinforce this pattern. Commitments by Acting President Delcy Rodriguez to pursue amnesty measures and reopen channels with the United States, including the reopening of the U.S. Embassy in Caracas, underscore how economic and maritime pressure are reshaping political engagement even in the absence of military action. Oil flows remain a central bargaining lever.

Coordinated DPRK-Risk Activity Inside Japan’s EEZ

Windward’s Early Detection identified a sharp behavioral anomaly in Japanese waters following North Korea’s ballistic missile tests on January 27.

Between January 28 and February 4, vessels with DPRK sanctions risk drifting inside Japan’s EEZ increased by 429%. Nine DPRK-risk vessels were detected, compared to a baseline expectation of 2.

The behavior was coordinated. Two DPRK-flagged vessels sailed in tandem within Japan’s EEZ, maintaining parallel routes and synchronized movement patterns for several days before splitting and exiting on February 4.

Drifting in isolation is not unusual. Combined with sanctions exposure, timing, geography, and coordination, it becomes a materially different signal. Population-level detection makes it possible for these patterns to surface early, before escalation manifests through interdiction or confrontation.