Let us begin with a short introduction.
On the 'Polish roll' (swe. Polska rulet), a panoramic painting created in 1605 and portraying the arrival of Costance of Austria to Krakow, where she was to marry Sigismund III Vasa, then king of Poland. This Painting shows Polish cavalrymen including some using a single wing mounted to the back of the saddle (most notably the royal standard-bearer). This painting, a first depiction of winged hussars, by the way, is a good proof that the wings were most definitely used during parades for decorative purposes. Charles Ogier, visiting Poland in 1635 wrote wrote about military parade: 'Hussars, the most prestigious nobility on superior horses, in richly ornate armours; skins of lions, tigers and leopards flow from their backs. They carry enormously long lances with pennants. On their shoulders they carry imposing wings'. On the other hand, Guillaume de Beauplan, cartographer and engineer in Polish service in the years 1630–1648 left many information about Polish troops, including hussars but he never mentions wings. This corroborates the theory that wings were used predominantly on parades, but were used sparsely (or at least not that often) in actual combat.
On a painting 'Battle of Klushino') created by Polish painter Szymon Boguszowicz in 1620, most hussars do not have characteristic wings and several figures in the central part of the painting are shown with black feathers adorning their backs. This is an important clue that wings were not used universally, as the painting renders most military details quite precisely and was created under the supervision of hetman (chief of command) Stanisław Żółkiewski who was commanded Polish troops during the battle. Hussars are also portrayed without wings on the 'Battle of Kircholm 1605 AD' by Pieter Snayers whose representation of the military equipment is considered accurate. In rare cases when hussars are depicted with wings, they are most often shown mounted to the saddle rather than the armour. Woodcut in the book 'Wake-up call for glorious sons of Polish Crown to the military service' by Wojciech Rakowski shows very detailed and accurate depiction of Polish hussar, but the only feathers are seen on the helmet. Also Szymon Starowolski in his book 'Eques Polonus' published in 1628 wrote 'hussars put feathers on their heads and heads of their horses alike".
As I wrote above, wings used by Polish troops were depicted for the first time in 1605. There are, however, several slightly older sources showing elaborate wings and skins of exotic animals used by Turkish skirmishers, commonly called deliler (tur. madmen, maniacs) usually used for quick raids and ambushes. One good depiction comes from Codex Vindobonensi (1590) and etching made by French geographer and traveller Nicolas de Nicolay for his 'Les Navigations, pérégrinations et voyages faicts en Turquie' published in 1579. Given that Poland was frequently involved in wars with Ottoman Empire in 16th and 17th century, we can safely assume that the wings could have not been used for any psychological effect when facing Turks for whom this would be a familiar rather than unsettling experience. And there is no sources stating that hussars' wings were devised with a wars with different enemy in mind (e.g. Russia or Sweden). Swedish painter, Johan Philipp Lemke, portrayed Polish Tartars equipped with fall wings apparently fastened to their backs ('Skirmish with Polish Tartars'), but veracity of this depiction was disputed as Lemke was not familiar with Polish armours and uniforms and could have conflated the image of Tartars with that of other kinds of Polish cavalrymen.
Informations about hussar's wings, although not that uncommon, give pretty little insight into their function. There most common theories are:
They were used to protect hussars from being strangled with a lasso, frequently used by Tartar riders.
They had a significant psychological effect as their sound was intimidating to enemies and especially their horses. Some also argue that their strange sight was by itself intimidating to horses.
They made the troop of hussars seem bigger than it really was, what made it difficult to estimate actual strength of Polish troops and increased the chance of enemy fleeing.
They were used for decoration only with a small psychological effect any non-standard or flamboyant elements may have on enemy.
So, let's go through them one by one.
#1. This is unlikely, mainly because Tartars were employed mainly by Ottomans who were definitely not the only enemies Poles fought in 16th and 17th century. If this was the reason for the use of wings, they would have not been used in combat with Swedes or Russians, also frequent opponents of Poland in the aforementioned period. Additionally, wings were usually depicted as being attached to the saddle rather than to the armour, what would make them illy suited for the purpose. And last but not least, it is rather unlikely that no other army regularly fighting with Mongols or Tartars, either in Europe or Asia even invented anything like it.
#2. This is another unlikely theory. It is true that Jean François Regnard, French traveller, wrote in 1681:
> "Retainers of these soldiers ride before the regiment, lance in hand and it is most curious that they have wings mounted behind their backs and on opportune moment they can break into enemy ranks using said wings to wreak fear among enemy's horses that are not accustomed to such a sight and thus make way for their masters who are moving close behind them".
But as common reason suggests and modern reconstruction prove, the sound given off by feathers is completely insignificant and would simply drown in the cacophony of war. The thundering sound of thousands of horses moving towards enemy would alone be enough, not to mention gunfire, shouts, flapping of flags and sound of trumpets and whistles used to convey orders. Also, there are no contemporary sources that would attribute breaking of enemy lines to the psychological effects caused by alleged sound of the wings.
#3. There may be some truth to it, but as hussars were attacking in relatively loose formations, small wings would give little to no effect. Most descriptions showing the wings as big, reaching from the small of the back to a good foot above the rider's head are products of 19th-century imagination. Virtually all such exhibitions in museum are also either 19th century falsificates of modern reproductions. Contemporary pictures depict wings as much shorter, located in the axis of the saddle and basically invisible from the front. Capes and feathers decorating helmets would give the same effect without any drawbacks of the wings. It should be also noted that big, double wings would make it hard to properly attack with a sabre with an overhead slash, very common way of attacking infantry. Sure, sabre was only a sidearm of the hussar, but such a drawback would most likely have not been taken lightly.
#4. From all popular theories, this one not only makes a lot of sense, but is even backed by some evidence. Royal rulings created by Stephen Bathory in 1576 and detailing equipment of the hussars state that: 'Captains will look for brave and strong horses, they shall wear apparel in Hungarian manner and over it they shall wear strong iron arours, helmets, iron gauntlets, lance, sword called kontsezh [Bathory was Wallachian and probably local name for a tuck was a novelty to him], carbines hung at the saddles and lastly, for their own splendour and fear among the enemy, feathers and other adornments as per each Captain's desire'.
As noted above in case of 'deliler' Ottoman cavalry, and practices of Swiss and German Landsknechte or Ottoman Janissaries, adorning armours and horses in flamboyant way was definitely not uncommon among elite troops. It is quite possible that 'non-standard' look of such soldiers was enough to shake the morale to at least some degree, as 'strange-looking' could mean 'elite'. And often it did.
On a practical note, it is worth noting that in 17th century Polish hussars have been commonly adopting karacena*,* i.e. lamellar armour, allegedly modelled after Roman lorica squamata, due to popularity of Roman themes and notions that Polish nobility are direct descendants of ancient Romans of Greeks, which, although completely ahistorical, were nevertheless popular. Lamellar armour, made of leather and metal scales made attacking an element as large and heavy as wings almost impossible. Conversely, a plate armour accommodating stiff wooden wings frames with more than one point of attachments on different armour elements would severely hinder the ability to bend or twist the body, gravely limiting the range of movements what could have fatal consequences in combat. This corroborates the the theory that the wings of 17th century hussars were either used for parades only and in combat they were either removed or replaced with wings mounted to the saddle or small adornment worn on pauldrons or an uppermost band of the back armour.