The A-10 warthog: raising depleted uranium’s threshold of acceptability
Speaking to the blog War is Boring, a Pentagon spokesperson justified this week’s decision by the US not to arm its A-10 gunships flying missions over Iraq and Syria with DU by explaining that: “The [DU] ammunition is developed to destroy tanks on a conventional battlefield. Daesh [Islamic State] does not possess large numbers of tanks.”
It’s certainly true that the 30mm PGU/14B DU round for the A-10 Warthog gunship was originally for destroying tanks. Developed in the Cold War, it was the first DU round to enter regular service. The thinking behind it was that if you wanted to stop a Russian tank column in Europe, one of the best means to do so was to attack from the air with armour-piercing incendiary (API) ammunition, as tanks have thinner armour on their top surface.
The gun, the ammunition it fires and the A10 aircraft itself were all tailored to this role. However, with the end of the Cold War, the A-10 has repeatedly found itself, and its standard combat load of mixed DU and high explosive incendiary (HEI) ammunition, in other roles. Unlike other DU firing platforms, once airborne the pilot cannot choose between DU and HEI ammunition, as it is loaded prior to take-off. Capable of loitering above the battlefield in a close air support role, A-10s often attack targets of opportunity, many of which bear little resemblance to “tanks”. Has this made the A-10's DU ammunition something of a political liability?
In the 1991 Gulf War, the US military fired more than 5,000 Maverick air-to-ground missiles, from both F16s and A-10s. It has been argued that these were the real tank killers in Operation Desert Storm, with fewer than one in seven Iraqi tanks destroyed by A-10s using DU. A range of other aircraft also engaged Iraqi armour, using a variety of guided bombs and missiles. Nevertheless A-10s still managed to fire 782,514 30mm DU rounds during the conflict, amounting to 236,319kg of DU. As the US has never released targeting data for the conflict, it is unclear what the range of targets attacked was but it is unlikely that targeting was restricted to tanks, given the widespread use of Mavericks and other ordnance and the comparatively modest number of tanks destroyed with DU.
A warehouse, mortar positions, weapons storage bunkers, a 120mm artillery piece and a mobile anti-aircraft gun were all among the targets attacked with DU by US A-10 gunships acting under NATO auspices in Bosnia between 1994-5. This information is from the coordinates that were eventually released by NATO in 2001, after repeated interventions by the then UN Secretary General Kofi Annan. It was data that was required by the UN Environment Programme to facilitate its assessment into the legacy of the weapons’ use in 2003. The coordinates included just one T55 tank, though others were present at a repair facility near Sarajevo that was repeatedly struck.
Serbian military undertaking an assessment for DU.
In the 1999 Kosovo War, NATO is reported to have destroyed just 14 armoured vehicles in the 38,000 sorties flown by all aircraft. Of the 112 sites in Kosovo, Serbia and Montenegro where A-10s used DU, the vast majority of targets were not tanks, or even the tank decoys used by the Serbs. A radio transmitter, barracks and non-armoured vehicles were all among the opportunistic targets attacked, although the exact nature of the majority of targets is unclear as NATO did not release information on target type.
A-10s came late to the conflict in Afghanistan but have been active in ground support operations there since Operation Anaconda in 2002. Questions remain over whether the A-10s have used DU in operations – some of the US’s ISAF partners certainly feared that they had and warned their troops accordingly. At the beginning of the conflict in 2001, it is thought that the Taliban had just over 100 armoured vehicles, a number that was rapidly decreased, but they were ultimately of limited use in the guerrilla fighting that followed. USAF images of A-10s being loaded published in later years suggest that only HEI ammunition was in use during Operation Enduring Freedom.
Still from CNBC's recording of an A-10 strafing the Ministry of Planning in Baghdad in 2003 (http://youtu.be/8_2Vz_x1LdM). Clue: this is not a tank.
A-10s were also active during the 2003 Iraq War, once again, the US has refused to disclose targeting data but a handful of coordinates obtained by PAX in 2014 provide a glimpse into the diversity of target types A-10s had engaged. The notorious strafing of Baghdad’s Ministry of Planning had already been documented by media present during the raid but the new data showed buildings, trucks and un-mounted troops had all been attacked with DU, often in urban areas.
In 2011, A-10s were deployed to Libya, a country which at the time had a considerable quantity of armour, although one which also had extensive air defences, against which the A-10 is vulnerable. Airstrikes had sought to neutralise these defences in the first fortnight of the intervention, prior to the arrival of the A-10s. ICBUW raised concerns over the possible use of DU by A-10s and parliamentary clarification was sought in a number of countries. When challenged on the issue, the Pentagon denied that DU had been used but refused to rule out its future use. As it transpired, the A-10s were only active for a short period of time before being withdrawn when the Obama administration elected to, publicly at least, take a back seat in favour of French and UK leadership of the operation.
Changing procurement policy
In 2010, ICBUW revealed that a decision had been taken in the US to phase out medium calibre DU ammunition. This would include 25mm ammunition in use by the Army’s Bradley fighting vehicles, the Marine Corps Light Armoured Vehicles and the 30mm rounds used by the A-10s. A time frame for the phase out was not provided but it was evident that the environmental burden of range contamination and increasing global pressure on DU had played a role in the decision. An earlier global phase out of the 20mm DU rounds used in the naval Phalanx system had taken many years.
In 2008, General Dynamics proposed an improvement to the A-10’s PGU-13/B HEI ammunition. This included increasing its weight and therefore its effective range so that it more closely matched the PGU-14/B DU round. Interestingly, the new variant would utilise tungsten to increase its mass but it was specified that it would be low cobalt tungsten. Cobalt had by that time been implicated along with nickel in military tungsten alloys that were found to be acutely carcinogenic in rats. The proposed alloy would use iron instead of nickel and the round would also have a new incendiary fill.
In 2011, General Dynamics and Alliant Techsystems won production contracts for new PGU-13D/B HEI ammunition for the A-10, and for the upgrading of existing stocks of PGU-13B. It is unclear whether the design proposed by General Dynamics in 2008 was utilised in the PGU-13D/B but if it was, the upgrade could potentially make up for any loss of effectiveness from losing the controversial DU variant. PGU-13 ammunition is still being procured as of federal year 14, some of which is for overseas contingency operations, although no budget has been sought for federal year 16. The 2011 contracts were the first in 20 years for production of the PGU-13.
Meanwhile the future of the A-10 itself is in doubt. Plans to retire the 285-strong fleet are well developed and are now the subject of intense wrangling in Washington. They remain popular with parts of the military but have also been the cause of more friendly fire deaths than any other US aircraft. Armed drones and the joint strike fighter are being pushed to fulfil the role it would vacate.
It’s the tanks, stupid
Four decades on, and DU was still controversial. When news of the decision to deploy A-10s to Iraq and Syria broke last December, a Pentagon spokesperson told journalist David Swanson that: "There is no prohibition against the use of depleted uranium rounds, and the [U.S. military] does make use of them. The use of DU in armour-piercing munitions allows enemy tanks to be more easily destroyed."
On the issue of prohibition, while lawyers still enjoy arguing over whether DU is specifically prohibited under existing international humanitarian law or not - something which says more about the law than it does about the acceptability of DU, a 1975 legal review of the weapons did recommend restricting the use of PGU-14/B ammunition to armoured targets. In considering the legal prohibition against unnecessary suffering and poison, the review suggested the following restriction: ‘This munition is designed for use against tanks, armoured personnel carriers or other hard targets. Use of this munition solely against personnel is prohibited if alternative weapons are available.’
Because DU rounds are incendiary as well as armour piercing, and conscious of the mid-70s global political concern over napalm, the review also noted that: ‘These munitions are incendiary in nature. Accordingly, they may cause fires which spread, thereby causing potential risks of disproportionate injury to civilians or damage to civilian objects. Precautions to avoid or minimise such risks shall be taken in the use of this weapon, or alternative weapons should be used.’
A working group that had been established prior to the review had also found that ‘significant impact can occur in the event of the uncontrolled use of DU depending on local conditions’, this was due both to DU’s chemical and radiological properties; risks that were identified as being potentially dangerous for civilian as well as enemy populations. However, the review found that the risks were ‘not necessarily disproportionate to the military advantages secured by the ammunition’, particularly if their use was restricted to ‘hard targets’. It concluded by warning that the widespread use of DU would be ‘seized on by potential adversaries for propaganda purposes’. Clearly, and unsurprisingly, the intrinsic public unacceptability of using radioactive materials in conventional munitions was well understood from the outset.
Reviewing past A-10 deployments and the fragmentary data available on the types of targets selected – disproportionately unarmoured, and their locations – commonly in built-up areas, it becomes clear that the legal restrictions on use have not been followed. Indeed the inability of the A-10 pilot to select between DU and HEI rounds once airborne, combined with the tactical loitering role of the A-10, pretty much guarantee that the recommended restrictions governing DU use will be breached. Given the experience of the 1991 Gulf War and the use of Maverick missiles it could also be argued that the comparative utility of DU should also be questioned, altering the balance of the conclusions in the 1975 review.
Returning to the question of the current operations in Iraq and Syria, armoured vehicles are in use by Islamic State - ironically some of these are vehicles provided by the US and captured from the Iraqi Army. If the PGU-14/B is as effective as its proponents claim, why not use it? And why wasn’t it used in Libya, against a dictator who had spent several decades building up a vast arsenal of armoured vehicles?
Of norms and noise
In a May 2008 report, the US Army Environmental Policy Institute advised that: 'the military should continue pursuing R&D for substitutes [to DU] and be prepared for increased political pressure for current and past battlefield clean-up.' That year, 94% of the European Parliament’s MEPs had called for a moratorium on the use of DU, a year previously, Belgium had become the first country in the world to ban it and a new United Nations General Assembly resolution on the issue had been passed by 136-6.
Belgian parliamentary hearing that secured its national DU ban in 2007.
Since then four more resolutions have been passed after they became biennial in 2008. While non-binding these have helped establish that the use of DU carries with it a potential health risk to civilians, soft norms on transparency and the transfer of targeting data, the need for precautionary approaches to post-conflict contamination and, most recently, the need for international assistance for states affected by DU. Support for the resolutions reached 155 in 2012, with the UK, US, France and Israel the sole opponents since 2008. Nevertheless, fixed obligations for the post-conflict clearance of DU are still conspicuous by their absence.
In spite of DU’s impressive ability to self-stigmatise, the determined defence of its use by its chief advocates has seen a number of EU states and NATO members and allies unwilling to openly criticise it. Though notably they haven’t sought to procure the weapons, do not allow it on their ranges and in the case of Canada and Australia, have legislation in place barring their uranium exports from being used for its production.
Internationally isolated and growing ever more conscious of the opprobrium associated with the use of DU, has global opposition begun to establish a threshold of acceptability for DU use? In the case of the A-10, where long-standing regulations on DU use are likely to be breached and where the destruction of armour can be achieved with missiles and bombs, is 30mm DU worth the political headache? Particularly when the majority of targets that A-10s have historically engaged in close air support operations can be tackled with HEI alone?
It may take another conflict or a change in the US’s official line to determine whether Libya and the current conflict against IS are signs of a change in policy over DU, or simply the result of factors specific to each conflict – such as Iraq’s 2014 call for a global DU ban. Nevertheless it seems reasonable to assume that the US is finally realising that the majority of the world view the use of DU in conventional weapons as unacceptable and that their renewed use would do little more than harden that opposition.