Tier I – High Priority
This covers the areas that are “must haves” for armor, the areas where any injury is likely to be fatal. Specifically, the head and the torso, both of which contain vital organs.
Tier IA – Very High Priority – Head
While the above may imply that head and torso armor come in a package, this is not actually true. Be it antiquity or modernity, head has received clear priority over the torso. While brain is protected by the skull, there is no muscle beyond the bone, and brain itself is a very sensitive organ. Consequently, head is very vulnerable to damage, especially the blunt force trauma. What this means is that cranial protection was the first on the list when considering any sort of protection.
In fact, soldiers tended to prioritize metal head protection over
any kind of body protection, even though textile armor was much cheaper than metal helmet. Helmets were among the last armor to be abandoned with advancements in gunpowder, and the first armor to return – though nature of trench warfare may have played some role in that as well.
Tier IB – High Priority
Torso is next in terms of priority. It contains all the vital organs that are not brain, as well as a mess of important veins and arteries. When it comes to torso itself, chest usually takes priority over the belly – both because it contains more crucial organs, and because it is easier to armor due to not being so flexible. There are exceptions to this – some armors preferred providing plate protection to belly over the chest, but in general, rigid defences tended to first appear in the chest area. Body armor also tended to cover the front of the body first, with back being covered later.
This armor also covered the chest and the belly, but not the hips or thighs. Greek and Roman muscle cuirass, Greek linothorax and Roman lorica segmentata all terminate at the natural waist (narrow region just above the hips), with protection for lower torso and upper thighs being provided by a sort of a hanging skirt. Early medieval plate cuirass also terminated at waist. Poor Romans in the early Republic would wear a helmet, a shield, and a pectoral – a metal plate covering the chest right above the heart – but nothing else.
There are several reasons for this. Hips and upper thighs are much more difficult to armor without impeding mobility (in fact, anything below the ribcage is difficult to armor without impeding mobility to at least some degree). Hips also contain a lot of bone and less vital organs. Nature of melee combat also means that greatest threat is always to the head and the chest, as short
weapons struggle to hit targets lower at the body. Even with longer weapons, such as spear which has no trouble reaching hips or thighs, attacks there are less likely.
Tier II
Second tier defenses are basically extension of the first tier defenses. They cover hips, upper thighs and shoulders. All three areas are also tempting targets: they are not much more mobile than torso itself, and still have high potential of disabling the target. They are also difficult to armor as they contain the joints whose mobility simply cannot be restricted.
Ancient armor that had rigid protection only for the chest still did what it could to protect these areas as well. This was often done by attaching pteruges – hanging strips of leather attached to armor. Mail armor –
lorica hamata – extended the mail skirt down to knees, and added second layer of mail to protect shoulders from downward attacks. Similarly, European
almain rivet – mass-produced plate armor for
pikemen – typically consisted of a helmet, breastplate, and tier II defences – shoulder protection (pauldrons), hip protection (fauld) and thigh protection (tassets).
Historically, one never sees Tier II protection without full set of Tier I protection. But fantasy often opts for so-called “doughnut” armor, where person has plate limb defences, but only mail or non-rigid textile armor for torso. This is likely a consequence of interpreting pictoral evidence such as funeral effigies, where torso plate is often covered by textile (whether by a surcoat or by a jupon), or else torso armor is a brigandine or other sort of semi-rigid body defense where metal protection is underneath textile or leather fronting. These can often make it seem like soldier is wearing plate limb defences and only non-rigid torso armor, but it should be repeated – this was never really the case.
Tier III
Third tier armor is the least important, but not necessarily the most rare. In fact, lower leg and shin protection is seen just as often, and sometimes more often, than some elements of the Tier II protection.
Reason for this is the shield. Shields rarely cover the lower part of the leg, which besides has to be forward for balance. This makes lower leg a tempting target, and greaves are a common defense for Greek and Roman soldiers, and appear quickly in Middle
Ages as well (mid-13th century, whereas plate cuirass appears only in mid-14th century). For comparison, soldiers who often fought under protection of large pavises often had no leg protection at all.
Legs and arms, requiring significant mobility yet being difficult to hit, were some of the last areas of body to be armored. Even lower priority was given to feet and hands, for similar reasons – even when long-sleeved mail was widespread, it took time for hand protection to appear.