Tribesmen loyal to the Houthi movement mark 1,000 days of the Saudi-led military intervention in the Yemeni conflict, in Sanaa on December 21, 2017. Photo: Reuters / Mohamed al-Sayaghi

The Iran-backed Yemeni Houthis have captured a US Navy underwater drone. The navy says the drone was part of a “meteorological study,” a lame excuse for carrying out a secret operation along Yemen’s coast. So what was really going on?

The drone is a Remus Model 600. It is manufactured by Hydroid in Pocasset, Massachusetts, in the northeastern part of Buzzards Bay.  Hydroid was acquired in 2008 by Kongsberg Marine of Norway for US$80 million. Its products are used in commercial and military applications; in today’s marketplace Hydroid is mainly selling to the US and other navies. The Remus Model 600 is used primarily for mine countermeasures and for littoral battle-space sensing.

The Remus 600 operates autonomously, meaning that it is programmed for a mission before it is released. The mission can be changed or modified, if desired, through an acoustic communications link provided the mother vessel (a ship or submarine) is reasonably close by, since acoustic signals are limited in range. Should the Remus 600 get into trouble, for example experience a technical fault or run into some kind of barrier, it will surface and communicate through a wifi signal. The Remus has a link to the Global Positioning System (GPS) and can transmit its coordinates if it surfaces.

We don’t know very much about the Houthi capture of the US Navy Remus 600, but we can make some informed guesses. The first is that the Houthis were prepared to ferret out the Remus or vehicles like it.  You don’t have on hand swimmers and wetsuits and other SEAL-type paraphernalia unless they are pre-positioned. This means that the Houthis were expecting some kind of seaborne military operation, and they were on hot standby to interdict an underwater spy device.

It is unlikely that the Houthis’ swimmers were just lucky in grabbing the Remus 600. They clearly captured it in shallow water, probably in a harbor. Either they were watching Remus operations over time or they had help from outside (for example, from Iran or Russia or both), or they had sensors planted in their harbor capable of picking up the Remus (not an easy task if it can actually be done) or they had intelligence.

The best guess: The US vessels dropping the Remus into the water were observed, enabling the Houthis to figure out where the Remus was heading. The alternative possibility, that the Remus had a technical fault and it surfaced, cannot be ruled out either. We just don’t know the answer.

Capturing the Remus drone will give the Iranians some ability to clone the device, although they still won’t have the software needed to program it. But that should not be much of a barrier for them. But this still leaves open the question of what the US Navy’s Remus operation was about

Capturing the Remus will give the Iranians some ability to clone the device, although they still won’t have the software needed to program it. But that should not be much of a barrier for them. And the Russians, if they are interested, also will have a chance to evaluate the Remus for the same purposes.

But this still leaves open the question of what the Remus operation was about. If it was mine clearance, then is it possible the Saudi-led anti-Houthi coalition was planning a military operation from the sea and needed to make sure the path was clear to bring in troops and supplies.

This would surely not be the first time.

Lurking behind this is the tragedy of the HSV-2 Swift. That was a very fast and relatively large catamaran ship originally built by Incat in Australia. After the US Navy acquired it in 2003, the navy’s Sealift Command operated the vessel for 10 years. Then it went out of service in 2013, replaced by another Incat-built catamaran.

In an unusual move, in fact a strange one, the Sealift Command leased the Swift to an organization in the United Arab Emirates called the National Marine Dredging Company. According to various news reports, the Swift was shuttling supplies and passengers between the UAE and Eritrea on the one hand and to Aden on the other.

So-called independent experts speaking on Iranian TV have said the Swift was moving troops from a training base in Eritrea to Aden (southern and eastern Yemen), controlled by the government of Abdrabbuh Mansour Hadi backed by Saudi Arabia and its allies. According to Aden, the ship was evacuating wounded persons and bringing in humanitarian supplies.

The problem is that the Swift was nowhere near Aden. It was just off the coast of Houthi-controlled areas north of the Bab (Strait) el-Mandeb close to the Port of Mocha on the Red Sea.

HSV-2 was struck by a Houthi-fired Chinese-made C-802 missile. The C-802 is a smallish surface-to-surface missile that can be fired from land or by ships. The Iranians have C-802s mounted on their small, fast patrol boats – the same boats that frequently harass US ships in the Persian Gulf. The warhead of the C-802 is designed to fragment to cause additional damage and is known as an explosively formed penetrator (EFP) warhead. Photos of the Swift hull after the missile strike and fire show a signature typical of an EFP round.

Because the Swift was made of aluminum, the vessel suffered severe damage. While it did not sink, there were many casualties, and the hulk of the vessel was eventually towed away and the Swift was scrapped.

(Among other things, the Swift was the precursor design for one of the two Littoral Combat Ship designs. The attack on the Swift confirmed what apparently the US Navy chose not to know, that aluminum ships are great targets for cheap Chinese missiles and the design is not suitable for combat operations. Even so, the navy is still building them.)

The Swift was intended to carry out a military operation to grab control of the Port of Mocha. It didn’t happen because the Swift disaster exposed the operation. Is there now preparation under way for yet another try at getting control over critical Houthi territory? The presence of the Remus 600 suggests this may be the case, even though the exact location of the Remus when it was captured isn’t yet known.

What can be said is that Houthi (read also Iranian) control of the Red Sea coast gives them potential control over the strategic Mandeb Strait. It is also the gateway to the inland city of Sanaa, the historic capital of Yemen that is controlled by the Houthis.

Were an invasion to be set up through one of the port towns, there are adequate roadway links to move forces and heavy equipment in under an effort to trap the Houthis and try to eliminate them as a threat to Saudi interests. An invasion of this kind makes sense on paper because the Iranians would be very hard pressed to support or resupply the Houthis if the roads are effectively blocked.

Whether in fact the Saudis and their coalition partners are really capable of such an operation is open to question, given their rather sloppy performance using air assets that have tended to kill many civilians but not stop the Houthis from expanding their operations in Yemen.

We will have to wait to find out if the presence of the Remus 600 has anything to do with future military operations in Yemen. Whether yes or no, sooner or later the United States will have to decide whether to let Iran establish a strong military presence in Yemen sufficient to block transit in both the Persian Gulf and the Red Sea. So far the level of US commitment has been very limited, but it cannot long stay on the sidelines providing only “technical” help to its allies.

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Stephen Bryen

Dr Stephen Bryen has 40 years of leadership in government and industry. He has served as a senior staff director of the US Senate Foreign Relations Committee, as the deputy under secretary of defense for trade security policy, as the founder and first director of the Defense Technology Security Administration, as the president of Delta Tech Inc, as the president of Finmeccanica North America, and as a commissioner of the US China Security Review Commission.

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