Subsea Cables in the Red Sea  

Key Judgments:

1. The Houthis’ capability to attack subsea cables in the Red Sea is dependent on Iranian intelligence.
2. There is a realistic probability that the subsea cables will be attacked. Severe disruption, however, is unlikely.

Since October, the Houthi militants have captured the world’s attention by their disruption to the critical shipping corridor in the Red Sea, significantly affecting global commercial shipping and energy flows. Recently, however, new concerns have been raised about a different target in the Red Sea: the subsea fiber optic cables that connect Asia and Europe. In December, a Telegram account linked to the Houthis posted a photo highlighting around a dozen of these subsea cables, with threats against them being shared and amplified by Iranian backed militias, including Hezbollah. These subsea cables carry nearly all the data and financial communications between these two continents, and therefore the Houthi’s interest in them as a target raises many concerns. The targeting of critical infrastructure is not a new phenomenon, as has been demonstrated by the destruction of the Nord Stream 1 pipeline and damage to Nord Stream 2 in September of 2022. This tactic has become of increasing concern in recent years due to economic reliance on international shipping and global connectivity, and the continental consequences to disruptions of critical infrastructure. The question that needs answering is whether the Houthis have the capacity to act on this threat, regardless of their intent.

In 2013, three Egyptian divers were arrested for attempting to damage some subsea cables off the coast of Alexandria, successfully damaging the Southeast Asia Middle East Western Europe 4 (SEA-ME-WE 4) cable and affecting data traffic in Egypt. This demonstrates the relative vulnerability of these cables, being susceptible to damage by just three scuba divers. The Red Sea itself averages a depth of 500 meters, with a maximum depth of 3,040 meters. Whilst the initial thought might be that the Houthis, or even Iran, do not have the appropriate subsea capabilities to target this critical infrastructure, the 2013 incident highlights that advanced capabilities are not a prerequisite to conducting an attack on the cables. With sufficient intelligence of cable locations in shallower depths, an attack on these cables appears plausible.

The Houthis have been armed and trained by Iran since 2015. In a report published by the Defense Intelligence Agency in the US in February of 2024, imagery intelligence was used to demonstrate this connection between the two entities, showing us how the Houthi missiles that are currently being used are direct reworks from Iranian missiles paraded during military exhibitions. This Iranian support extends to the sharing of intelligence with the Houthis, as has been demonstrated by the presence of an Iranian military ship, the MV Behshad, in the Red Sea which the US claim is collecting intelligence on commercial shipping and sharing this with the Houthis to inform their attacks. Whilst the Houthis do not have the naval capabilities to appropriately collect intelligence amidst hostile navies, the MV Behshad may be able to supply the Houthis with intelligence on the ideal locations where a diver may be able to damage the cables. If this intelligence were to be provided, the Houthis will indeed have both the intent and the capability to conduct this attack, meeting the ‘threat’ criteria. This threat is amplified due to the consequences of such an attack. Whilst in peacetime, these subsea cables are often damaged as a result of fishing vessels or ship anchors dragging on the seabed, and most nations have standing units ready to repair these minor damages as and when they occur. In the Red Sea, however, the missile threat from the Houthis significantly degrades the ability to fix any potential damage to these cables, as the risk to the repair vehicle, which will need to remain still for several days to conduct the repair, will be too high.

Whilst the Houthis do in fact present a threat to these subsea cables, it is important to acknowledge that whilst one subsea cable is very vulnerable, there is a lot of resilience built into the system. Damage to one cable results in the rerouting of the data in said cable amongst the other cables in the network, therefore damage to any one cable will not severely affect the intercontinental data traffic. Also, individual divers will not be able to produce the widespread damage that would be possible if the Houthis had submarine capabilities, therefore reducing the scope of the threat.

To conclude, the subsea fiber optic cable network passing through the Red Sea is a vulnerable, critical infrastructure which the Houthis currently have the intent to target. With the support from Iranian intelligence, the Houthis are likely to obtain the capability to act on this intent, marking this issue as a significant threat, despite the resilience built into the network. As a result, the Houthis have a realistic probability to target these cables via diving operations in the shallower areas of the Red Sea. This threat is unlikely to cause severe disruptions to global data traffic, again due to the built-in resilience. A well-coordinated attack, however, certainly has the potential to do so. If this situation occurs, it will mark an escalation in the conflict between the West and the Houthi-Iranian alliance to new heights, and therefore needs to be monitored intently by Western forces in the Red Sea.