The battlefield is seldom a comfortable place, regardless of where it falls on the globe. Soldiers have to deal not just with the threat of gunfire and artillery, or improvised explosive devices (IEDs) – whether they lie in wait for approaching vehicles or delivered by remotely controlled drone – but also with the environment in which they find themselves. While shrapnel can shred flesh and shatter bone, heat and cold can also prove more than capable of incapacitating a soldier, or at the very least, hampering their efficiency.

After all, the danger that extreme weather poses to military operations has been well-known for centuries – it’s not for nothing that the Russian Winter is often referred to as ‘General Frost’ or ‘General Winter’, given its role in foiling invasions across the ages, including that of Napoleon and Hitler. However, weather doesn’t have to reach extreme levels to pose issues for militaries, even modern ones, and it is imperative that the clothing soldiers are outfitted with can perform at the highest levels under all manner of challenges.

Similarly, thick forest, moisture-laden tropics and hard-wearing mountainous regions all pose unique challenges for modern militaries, and these must also be borne in mind when developing combat clothing that will be used by armed forces across the globe. The British Army, for example, is deployed in countries as wide ranging as Iraq, the Falkland Islands, Cyprus, Estonia and Kenya, among others.

The price of protection can come at a cost. Heavy protective systems can present new challenges for soldiers who until recently were climbing mountainsides in Afghanistan, and it can boil the ones who wear them in the desert. Ceramic plates have led to comfort issues for smaller soldiers, especially women, sitting down in vehicles for hours-long convoys. Helmets can snag bergens when soldiers hit the dirt and go prone, making it harder for them to turn their heads and thereby hampering visibility. At the end of the day, a balance has to be found.

In search of balance

“Unfortunately, we can’t protect against all threats – it’s just not feasible to do so,” says Jon Russell, senior principal scientist, Physical Sciences Group at the UK’s Defence & Science Technology Laboratory (Dstl). “There’s a compromise between the level of protection both in terms of the actual threat level and the coverage to the individual, and the physical and thermal burden.”

As a result, combat clothing is generally designed to mitigate against smaller fragments – which Russell refers to as “secondary projectiles” – from a threat, such as improvised explosive devices (IEDs). With this in mind, the combat clothing Dstl is looking at comprises of relatively low-areal density protective material, which are acceptable from a comfort perspective to its users. These ‘human factors’ cover not just the physical burden of the clothing, but also the cognitive and thermal burdens.

A secondary benefit of defeating smaller fragments is the reduction in the amount of debriding that surgeons have to perform when cleaning and treating wounds. “This essentially involves surgeons removing fragments from the individual’s wounds to prevent infection,” says Russell. “It’s much easier if there’s a small amount of protection to help limit the depth of penetration of those smaller fragments.”

While every material has a ballistic property, the traditional polyester/cotton blend that makes up the regular clothing used by British Army soldiers has a relatively low one in terms of its ability to mitigate fragments. Combat clothing, on the other hand, makes use of high-strength fibres that offer improved ballistic properties within an acceptable weight limit.

“We can’t stop a bullet with low-weight materials,” explains Russell. “But we can stop a relatively small fragment going at a representative velocity, using those materials – while polycotton might not.” Even if these fibres fail to prevent penetration, they can lessen the residual effects, reducing the energy of the fragment and consequently its depth of penetration.

As a result, the fragment might only perforate a few millimetres, for example, rather than 10mm or more, reducing the risk of damage to underlying structures, and making the debriding process easier and thereby reducing the risk of secondary infection. Combat clothing also has non-ballistic requirements, specifically non-melt and non-drip properties – in the event of exposure to fire, such as a vehicle fire, for example, or a public order situation.

Dstl’s role in all of this is to conduct work in-house in order to advise the UK Ministry of Defence (MOD), crime and policing authorities, industry and other government departments on the nature of injuries from threats such as bullets, fragments or blast, and so on, and the levels of physical protection required to mitigate those dangers. And then, consequently, observing and analysing the resulting influence on soldier performance from a human factors perspective, once materials have been put in place to combat those threats. This process, Russell explains, ensures that UK soldiers “are provided with the best available solution and options”.

This involves close collaboration with industry partners to inform the development of combat clothing materials and in “trying to reset the nirvana of balancing protection, burden and mobility, while offering acceptable levels of comfort to the wearer, which is obviously paramount”, Russell adds.

However, sometimes issues you don’t foresee can lead to complications regarding that balance, where comfort or mobility can be compromised. When that happens, militaries need to be able to modify and adapt their combat clothing offerings, in order to best equip their soldiers.

The Virtus system

Back in January 2015, SOURCE – Israel’s largest tactical gear manufacturer and exporter – signed a multi-year contract with the UK MOD to supply integrated personal protection and load carriage systems to the British Military. This body armour system was known under the name ‘Virtus’, and was developed to withstand the challenges and needs of modern infantry soldiers, increase agility, and make it easier for soldiers to carry heavy burdens. Developed as a successor to the Osprey body armour, the Virtus system offers the same protection while being significantly lighter, moving more easily with the body and producing a slimmer profile. Virtus is also scalable, allowing it to adapt to the challenges of current and future operating environments and threats by adding or removing soft armour and hard ballistic plates.

However, that’s not to say that this new body armour system was without its own share of issues. Despite being designed to be lighter than the Osprey system it replaced, there were challenges when outfitting female soldiers, who became eligible for all roles within the UK military in 2018. In the summer of 2021, a new version of the Virtus system was trialled, with narrower straps and a shorter torso length and width, in order to increase comfort, fit and the range movement.

“The modifications to the Virtus scalable tactical vest (STV) focus on reducing excess material for the users – particularly for females – with ill-fitting or oversized STVs,” notes Russell. “We’ve conducted those human factors trials and we’re now procuring a number of those systems over the next 6–12 months with additional sizes.”

This is not unusual for combat clothing or military equipment as a whole – as a system sees active duty or use beyond its initial parameters, issues will inevitably arise, and therefore a modern military needs to be able to incorporate feedback from its soldiers and its industry partners in order to enhance and improve their equipment. Since the adoption of the Virtus system, it’s been issued to approximately 100,000 military personnel across all of the British services. This gave the individuals and units that used the first generation of Virtus to suggest modifications to the system to the MOD, which also adopted developments suggested by the manufacturer, such as load carriage systems.

“Some units and users have different roles and different equipment that we didn’t originally accommodate for, given that [the Virtus systems] was meant to be for high-readiness troops initially,” explains Russell. “The uptake of Virtus has been a lot wider and larger than initially planned, because of its popularity.” Other modifications make the Virtus helmet less prone to snagging when used by paratroopers, or minor tweaks such as a changeable cover for soldiers conducting peacekeeping operations.

“The key is good communication and links with the manufacturer to ensure [any issues] can be identified early on, and to get those better products or better modifications as soon as possible,” says Russell. “Equally, providing feedback to the manufacturer is also important – on what works, what doesn’t work, and so on.”

Integrating new systems with established ones

The development of any personal armour system requires a balance between the degree of protection and the degree of burden, but this can be complicated when integrating new systems with older ones, or also when updating systems. In evaluating such a system, Russell makes it clear that the MOD’s first priority is to evaluate what a soldier can accept from a wearability perspective in terms of physical and thermal burden, and comfort levels. As stated earlier, while it would be great to be able to protect a soldier from every threat they might face, in practice that is simply not possible – therefore, the MOD evaluates what is acceptable from a soldier’s perspective, and from there optimise the threat and coverage it can provide while also integrating effectively with other equipment.

“So, rather than just specifying ‘X number of layers of very highly protective material that’s very good at stopping the threat but is not very comfortable’, it will be the other way around,” Russell explains. To evaluate comfort, physical and thermal burden, Dstl use hardset measurements based on metrics for considerations such thermal stress, depending upon the type of trial. “We have something called the ‘Human Factors Assessment Framework’, which has three levels of assessment for a user trial,” Russell explains, before breaking the framework down.

The first level consists mainly of subjective feedback from the user, such as perceived exertion, discomfort and thermal stress. “They might say they’re hot, but without the ability for us to actually measure and quantify that,” Russell adds. Level three, on the other hand, is usually a lab-based trial where Dstl monitor a number of biological markers on the test subject, including heart rate, temperature and internal core temperature, among others. Level two, meanwhile, is a mixture of both. “We might, for example, record heart rate while they’re going over an obstacle course – and use a mixture of those types of tests and the subjective questionnaires with the user at the end.”

With all this in mind, Russell works to ensure that test processes and performance requirements ensure that items are tested as they’re intended to work and in a realistic representative and repeatable environments. However, tests can only take you so far, as Virtus has established – sometimes equipment is used in scenarios it wasn’t initially intended for. It’s up to militaries to ensure, therefore, that the testing they carry out mimic in-the-field conditions as closely as possible, and to swiftly work to address any issues that come to light after that point.

“With most things, it’s not until you’ve actually tried it that you find out the issue, and then try to mitigate those going forward,” says Russell. “Personally, I’m an advocate – when I do ballistic testing – of testing things as they’re worn, ensuring that you test them in realistic and representative ways to how they’ll see service.”


The number of military personnel that have used the Virtus armour system across all of the British services.



The amount by which the Virtus system is lighter and better fitting than the Osprey body armour it replaced.


The amount by which the Virtus helmet is lighter than the Mk7 it succeeds.