How the Houthis’ Maritime Targeting Evolved — Phases, Patterns, and Who’s Next

Yemen’s Houthi movement has turned maritime action into a calibrated instrument of influence. What began as local, opportunistic harassment of shipping has become a sequence of declared escalation phases, each widening who — and what — the Houthis consider legitimate targets. The International Institute for Strategic Studies (IISS) has catalogued these shifts; below is a synthesis of that analysis with practical implications for ship operators, insurers and policymakers.

Four (Actually five) declared phases — what changed and why

The Houthis have publicly announced or signalled changes in their maritime campaign, and those announcements map to distinct phases. The IISS breakdown (which you supplied) shows clearly how targeting criteria, weapon types and geographical scope have incrementally expanded.

Phase 1 — Initial calls to monitor and target Israeli ships (14 Nov 2023 – 8 Dec 2023)

Key message: the Houthis declared they would monitor the Bab el‑Mandeb/adjacent waters and not hesitate to target Israeli ships.

Targeting rule: Israeli‑owned ships transiting the Red Sea and Bab el‑Mandeb.

Trigger: The Gaza war.

Implication: This phase marked the public politicisation of maritime attacks — ships were now selected for perceived national association.

Phase 2 — Ban on ships calling at Israeli ports; threats to escorts (9 Dec 2023 – 17 Jan 2024)

Key messages: warnings that any ship heading to Israel (of any nationality) and ships escorting Israeli vessels were legitimate targets.

Expanded rule: Any ship servicing Israeli ports; escorts considered hostile.

Trigger: Interception of Houthi attacks by US warships (Operation Prosperity Guardian).

Implication: Targeting moved from nationality to function — port calls and escort behaviour now mattered.

Phase 3 — Explicit inclusion of US/UK-linked ships and geographic widening (18 Jan 2024 – 2 May 2024)

Key message: the Houthis said American and British ships were now within scope.

Trigger: Operation Poseidon Archer (international strikes aimed at degrading Houthi capabilities).

Implication: The campaign became explicitly anti‑coalition as well as anti‑Israeli, increasing risk to western‑flagged/owned tonnage.

Phase 4 — Broader sanctions on companies with Israel links; Mediterranean reach (3 May 2024 – 18 July 2024)

Key message: the Houthis announced a fourth stage targeting ships that “violate the ban on Israeli shipping,” and companies whose vessels call Israeli ports, and extended operations into the Mediterranean.

Expanded rule: Not only ships directly calling at Israel but all ships from companies with other vessels that called Israeli ports (effective 6 May).

Trigger: Israel’s offensive in Rafah.

Implication: Ownership and corporate linkage became explicit criteria — the threat now reaches beyond single‑ship attribution to corporate risk.

Phase 5 — New weapons and continued escalation (from 19 July 2024)

Key message: the Houthis announced a fifth stage and the use of “a new weapon” (advanced drones) and signalled further escalation.

Trigger: Houthi UAV attack toward Tel Aviv (19 July 2024).

Implication: Weapon sophistication (UAVs, ASCMs, and later ASBMs) increased both reach and lethality.

How the targeting profile changed — from opportunism to deliberate selection

Three clear developments emerge from the phased declarations:

1. From presence → provenance → corporate linkage. Early attacks targeted ships present in the wrong place. Later phases explicitly targeted ships because of where they called (Israel) or because other vessels in the same company had called Israeli ports. Ownership and commercial history are now operational inputs to targeting decisions.

2. From small arms → precision strike. Weapons progressed from small boats and RPGs to drones, anti‑ship cruise missiles, and (in the latest reported cases) anti‑ship ballistic missiles. Increased precision changes both casualty and insurance calculus.

3. From local waters → extended corridors. The operational area widened from Bab el‑Mandeb/Red Sea into the Gulf of Aden and, by declaration, into the Mediterranean — converting choke points into contested zones for international trade.

   
   

Which ships are most likely to be targeted next?

Given the declared criteria and observed behaviour, the following vessel categories face elevated risk:

• Ships that currently, recently, or historically called at Israeli ports. The Houthis explicitly link attacks to port calls; even indirect links within the same corporate fleet increase vulnerability.

• Vessels owned/operated by companies with other ships calling Israel. The fourth phase's corporate sanctions mean ownership/charter relationships matter as much as flag.

• High‑visibility commercial tonnage (container ships, bulk carriers, RoRo).These provide strategic disruption and media attention; they are preferred targets for maximal economic effect.

• Western‑owned or US/UK‑flagged vessels — especially those tied to military logistics or convoys. The third phase expands the threat to coalition-linked tonnage.

• Ships operating with irregular AIS behaviour (“going dark”) or that deviate from standard routing. Such behaviour can mark a vessel as irregular and draw closer scrutiny — paradoxically increasing the attention it receives.

• Escorts and vessels participating in convoy protection. Phase two messages treated escorts as legitimate targets; this increases the operational risk to naval assets and protected convoys.

  
  

Practical mitigations — what operators must do now

• Treat corporate port call histories as an operational risk factor. Screen ownership and sister‑vessel calling histories for links to Israeli ports; consider temporary commercial buffers.

• Avoid declared zones when feasible; increase transit speed and transparency where needed. Use recommended maritime guidance (UKMTO, MSCIO, national alerts).

• Harden vessels: proactive watch, physical barriers, citadel procedures, and consider employing accredited armed security where legal and feasible.

• Engage insurers and P&I clubs early about declared risks and receive guidance on rerouting versus additional premium exposure.

• Coordinate with naval coalitions and CMOs (UKMTO, MSCIO, national task forces) for timely advisories.

  
  

Conclusion

The Houthis’ maritime campaign is no longer random or purely opportunistic: it is a politically informed, phased campaign that targets ships by port history, ownership links and international affiliation, backed increasingly by sophisticated weaponry. For shipowners and operators the message is stark: commercial routing and corporate relationships now comprise part of a vessel’s risk profile. Understanding the declared phases is therefore essential — not academic — for every actor who moves goods across these vital waterways.