'Given Australia’s limited resource base, we must improve our ability to deliver these (deterrent) effects without seeking to match the capability of major powers. This includes developing capabilities to hold adversary forces and infrastructure at risk further from Australia, such as longer-range strike weapons, cyber capabilities and area denial systems.'
– 2020 Defence Strategic Update

The War in Yemen, which is now approaching seven years of conflict, continues to be a complex and bitter confrontation. A conflict littered with accusations of war crimes on both sides[1], the war in Yemen is responsible for one of the most significant humanitarian crises of the 21st century[2]. The main belligerents in the conflict are the Iranian aligned Houthi and the Saudi Lead Coalition (SLC). On one side is a non-state actor, while on the other are nations with access to some of the most advanced military technology available. By using an unconventional long range strike capability, the Houthi have consistently demonstrated an ability to penetrate modern air defences and achieve strategic effects despite being overmatched in technology, manpower and funding.

While the Houthi have used a variety of weapons for these strikes, One Way Attack (OWA) Unmanned Aerial Vehicles (UAVs) have proven to be a low cost, high payoff option to produce direct and in-direct effects. As the ADF grapples with the challenge of a ‘less remote prospect of high intensity conflict within the Indo Pacific’[3], the success of unconventional long range strike is a lesson which can be extracted from the war in Yemen. This capability would provide an asymmetric advantage to help balance the capability of major powers, be able to be developed and built in Australia, and be a force multiplier for the traditional long range strike capabilities the ADF is seeking to acquire.

Background

The changing strategic environment outlined in the 2020 Defence Strategic Update has been a key driver in Australia allocating billions of dollars to acquire a range of land, air and maritime-based long range strike capabilities. Commencing with the AGM-158C Long Range Anti-Ship Missile (LRASM)[4], these systems will enable the ADF to offer a credible force to hold adversary forces and infrastructure at risk, despite the increased prevalence of Anti Air/Area Denial (A2AD) systems in the Indo-Pacific. As recognised by recent announcements to develop a sovereign missile manufacturing capability[5], a key vulnerability of these capabilities is the supply chain due to the complexity and high cost involved. The COVID-19 pandemic and the recent blocking of the Suez Canal has shown the fragility of global supply chains. Maintaining a constant supply of necessary materials, let alone guaranteeing the ability to fully manufacture missiles, would be a significant challenge (if not completely impossible) if any conflict broke out. While the prospect of high-intensity military conflict is less remote than in the past[6], if major powers do come to conflict, given its relatively small size, the ADF will be required to produce an asymmetric effect. Australia does not have the resource base to be able compete with major powers and will likely not be able to replenish stocks of missiles quickly.

Prior to discussing what the ADF can learn from the employment of OWA UAVs by the Houthi, it is worth acknowledging other recent conflicts which have seen UAVs give a significant advantage. Analysis of recent UAV employment in the Syrian and Nagorno-Karabakh conflict[7] has demonstrated the significant asymmetric advantage to be gained at the tactical level. On the contemporary battlefield UAVs have been utilised to cue fires, launch their own munitions or act as a munitions themselves to inflict damage on armoured vehicles that far outweigh the loss of UAVs[8]. UAVs in these conflicts have been highly effective tactically; however, the Houthi have demonstrated their utility in long range strike. While there is merit in discussing the ADF increasing its use of UAVs on the tactical battlefield, this will not be the focus of this article.

Houthi employment of OWA UAVs

While the Houthi employ a number of unique systems for OWA UAVs, the more successful strikes appear to have utilised the Sammad-3 system[9]. Believed to utilise a simple petrol engine combined with GPS / gyroscope guidance, this system can carry an explosive payload of approximately 8kg over a reported range of 1500km[10]. Although the individual cost of this system is unknown, estimates have been less than $15,000 USD[11]. While there is a disputed claim of assistance from Iran in developing and manufacturing this system, the capability compared to cost outlay is still impressive. In 2021 the Houthi even claimed to produce a Sammad-4 with a range of 2000km; however, it does not appear to have been utilised for a strike yet[12].

Without recapping the entire background of the war or the evolution of the Houthi’s OWA UAV capability, the key points on the Houthi’s employment of OWA UAV are:

• Attack Profile. The Houthi effectively utilise their OWA UAVs as Cruise Missiles, launched against pre-determined coordinates and then flying at low level towards a target. Using commercial satellite imagery to determine coordinates, they are able to launch against area targets with impressive accuracy. GPS guidance and gyroscopes enable the Houthi to ‘fire and forget’, thus not requiring terminal guidance or operator control for the UAV to strike the target[13].
• Targeting. The Houthi have routinely targeted large static locations such as oil infrastructure, government/military headquarters and airfields[14]. While a specific attack will be discussed below, targeting of Saudi Arabia’s strategic assets through OWA UAVs directly and indirectly produces a disproportionate effect in relation to the cost of the system. While the explosive payload of the OWA UAV is relatively low, this is not a factor with the correct target selection. As shown by the Houthi, targeting locations where there is high likelihood of secondary explosions/fire or where superficial damage requires extensive repair is the most effective use of the OWA UAV.
• Tactics. Due to the relatively low cost of OWA UAVs, the Houthis are able to employ ‘swarms’ of up to ten UAVs. By using multiple attack headings, the possibility of overwhelming radars and penetrating air defence is increased[15]. The small cross section, low altitude and low speed also contributes to its success, as it is not a profile that modern air defence systems have been designed for. By using GPS / gyroscope guidance there is no ability to interrupt the link between the OWA UAV and a UAV controller.
• Support to traditional long range strike. The use of OWA UAVs is also complementary to more traditional long range strike capabilities such as ballistic missiles. By employing the tactics described above, this can increase the chance of the missiles penetrating air defence due to the confusion caused by OWA UAVs. Another tactic is to use the OWA UAVs to directly target air defence radars by attempting to fly into them[16]. Used as a Suppression of Enemy Air Defence (SEAD) mission, this not only creates a window for ballistic missiles, but takes a valuable finite asset off the battlefield for a period of time.
• Saudi response. The Saudis have been able to intercept some OWA UAVs, through either fixed wing fighters or concentrations of air defence systems. Evidence of this was a video of Saudi F-15s successfully intercepting Houthi OWA UAVs, released in late March 2021[17]. The cost of operating these types of defences however, is disproportionate to the OWA UAVs and ties down limited assets. For the F-15s, it limits these platforms to air defence rather than other mission types, such as striking Houthi locations.

The 2019 ARMACO attack

The highest profile and successful attack occurred on 14 September 2019, targeting the ARMACO facility in Abqaiq. While some of the details of this strike are disputed, the successful penetration of air defence and the effects are in no doubt. The attack utilised a combination of up to 25 OWA UAVs and ballistic missiles[18], and disrupted 50% of Saudi’s oil output and 6% of global supply[19]. In the aftermath of the attack the Houthi claimed responsibility; however, the US blamed Iran for launching the strike[20]. Regardless of the point of origin, the ranges are impressive with the facility being approx. 800km from launch locations in Yemen and 600km from launch locations in Iran. To contextualise this, Brisbane to Townsville is approx. 1100km, well within the capacity of the reported range of the Samad 3. To compare this to the long range strike capabilities the Australian Army may be seeking to acquire, the US M142 HIMARS that was demonstrated at the last Ex Talisman Sabre in 2019 has a maximum range of 300km[21].

The ARMACO facility was not an unguarded civilian site, and far from an easy target. The air defences surrounding the facility were extensive. The Saudi military had US Patriot Missiles, SkyGuard short range air defence (based on Oerlikon 35mm cannon) and French Shahine short range missile defence deployed around the oil facility[22]; however, it appears none were able to intercept any of the UAVs or missiles. Small arms were also ineffective, likely becacuse of the large number of OWA UAVs[23] and short warning time overwhelmed the defenders. While there are obvious differences between the platforms used, it could be argued that the air defence deployed around this single site exceeds the entire Australian Army’s air defence capabilities[24]. While the vulnerability of the ADF to UAVs needs to be addressed, it is also an opportunity as potential adversaries are likely to have similar vulnerabilities.

The success of the ARMACO attack and Saudi response has not led to assured intercept of OWA UAVs. Additional long range strikes occurred in June 2020 against King Khalid Airport and the Defence Ministry in Riyadh[25]. As recently as Feb 2021, the Abha International Airport was struck[26]. This suggests a vulnerability in capability that is being consistently exploited rather than readiness issues.