While I’m certainly not an expert on the concept, ideas surrounding martial race are something I engage with in in my PhD thesis, so I can provide at least a partial answer, with particular reference to Scotland (with Scottish Highlanders being one of the archetypical examples of a supposed ‘martial race’).

Ideas about ‘martial races’ emerge in the latter half of the nineteenth century as the product of a convergence of factors – notably the expansion of European empires and new ideas about race (influenced in turn by Darwinism). European colonisers – particularly the British – are looking for ways to explain different levels of military capability among their subjects. Heather Streets, one of the foremost scholars on the phenomenon, locates this in the aftermath of the Indian Mutiny of 1857, which had an unprecedented effect on domestic popular and official opinion thanks to the gruesome and shocking nature of the reprisals against British soldiers and civilians. Explaining the Mutiny – which had taken the British entirely by surprise –through racial differences became popular, particularly among soldiers. Hindus, particularly those of high caste, are imagined as unmanly, cowardly and treacherous, and are contrasted with those who stay loyal (such as Sikhs, another famous ‘martial race’). This way of thinking spreads across the British and other European empires, acting as a useful rationalisation for differentiating between races and their perceived capabilities. ‘Manly’ or ‘martial’ groups became favoured targets for recruitment for colonial powers. It should be noted that this kind of categorisation has a long history – Italians, for instance, have been viewed as inherently unwarlike since the sixteenth century or before. Yet new ideas about race – particularly conceptualising race as subject to a version of natural selection, in which ‘stronger’ races would inevitably conquer and displace weaker races – means that these ideas gain particular credence and substance in this period.

The question of whether these races actually WERE better fighters is much more difficult to answer. Naturally, whenever someone wanted to construct a racial hierarchy, they put themselves at the top (which is not to say that they weren’t anxious about it – the British, for instance, get very paranoid about perceived racial decline due to urbanisation and industrialisation in this period), so at least some of the claims were more than a little dodgy by default. You can see this when comparing various national mythologies about the First World War. Every nation has a battle they won (or distinguished themselves in), everyone claims to have had the best soldiers, or been regarded as ‘shock’ troops, or had the highest number of casualties (per capita, usually). No one who fought remembers their contribution as being ‘kinda middling, adequate I guess.’ For societies that value military prowess, there’s usually a way to spin things so that you come out looking good.

Much of the mythology also falls apart when you look closely enough. If we return to our Scottish Highlanders, it’s quickly apparent that most of these kilted warriors are actually from Lowland Scotland, which makes sense because that’s where most Scots actually lived at the time. This gets even more muddled by the wars of the twentieth century, where mass recruitment (and then conscription) blurs the lines even further, becoming impossible to maintain much geographic cohesion among new drafts. So, when we talk about Highland regiments distinguishing themselves at various battles, we’re hardly ever talking about actual Highlanders, or even Scots past a certain point.

On the other hand though, success in warfare has a close correlation to morale, which in turn reflects self-belief. In other words, if you believe that you’re better than your opponents, this is going to help you win. There might be many cultural, economic and other reasons why some groups are more militaristic than others. European colonialists might rationalise this as being inherently racial, but we might now point to other factors that can explain the same differences they observed. Not that this kind of thinking has disappeared – as any French people sick of being called cheese-eating surrender monkeys might attest – but that most people find it repugnant to view race in such explicitly hierarchical terms.