While I'm on the subject of Dragoons and what not, I thought it an apt time to discuss one of my pet peeves: the complete incomprehension of most modern military writers to understand just what in the heck a "Dragoon" is.
If you crack open a book or a web-page on cavalry (especially American cavalry) you will soon discover the term "Dragoon", and of course the author will make an attempt to define this rather unusual term for the reader. Usually they take it straight out of a dictionary, without ever bothering to check to see if the definition they've chosen to spout is in fact the proper definition for the era which they are writing about. What doesn't seem to be a commonly understood phenomenon is that terms change in their definitions over the years, and while they may mean one thing in one century, often as not mean something quite different in another. Thus the massive confusion.
In the early 17th Century, a "Dragoon" was the proper definition of Mounted Infantry. They were armed as Infantry, with an arquebus/caliver/musket and infantry accoutrements (such as a bandolier of chargers, etc.), were organized as Infantry with corporals, sergeants and ensigns, and acted like Infantry in the field. The only thing they did with horses was to ride to the battlfield and then dismount to carry on their activities. Dismounting one's Harquebusiers/arquebusiers á cheval was certainly commonly done, and the archers of the Kings of England were often mounted on nags for their Chevaucheé's, but as for orgainising mounted infantry on a large scale, the tip of the hat must go to the Admiral Gaspard de Coligny in the French Wars of Religion. He wanted to give some serious infantry firepower to his Cavalry-heavy armies as well as do something useful with his otherwise surplus numbers of Shotte. His successor in the Protestant Cause, Henri de Navarre, later Henri IV of France, followed this lead with his "Equestrian Army" (see the article "All the King's Horsemen" by my old friend Ron Love in the 16th Century Journal, 1992.) By 1600 this was well established, and as such was much discussed by military writers such as Sir Roger Williams, Johan Joachim von Walhausen and John Cruso. In the 30-Years War and the English Civil War they were an important part of any army in the field, both for scouting and skirmishing, but at times also taking part in Cavalry actions.
This seems to be a standard process, in that Mounted Infantry has a strong tendency to try to "improve their status" by doing less and less Infantry, and more and more Mounted as the years go by. There is a distinct disinclination to dismount and fight on foot, at least until another war comes along and the need is appreciated by all and sundry. Then, often as not, yet another new corps of "Mounted Infantry" is raised, and the old Mounted Infantry (by whatever name) gets to be Cavalry.
By the beginning of the 18th Century this trend was pretty obvious, and many of the European powers (such as Russia) had completely disbanded their "Horse" (i.e. "real" Cavalry) and converted all to Dragoons. The English followed suit in the early years of George 1st, interestingly enough because Dragoons cost less to operate than Horse. Thus, with the exceptions of the Household Cavalry, all British mounted units were now Dragoons, Dragoon Guards, etc. With the change in status, there was also a minor change in organization. Here to fore, Cavalry NEVER had a rank known as Sergeant. They had Corporals, and not many of them. Cavalrymen were the elite, and were understood to not need as much babysitting as Infantry were, thus the lack of need for such a rank. Besides, Sergeants were originally there to impose order in the ranks, and not simply discipline. Order as in, Ranks and Files. So along with the new lower status, Cavalry now received a new rank, Sergeant. (You can tell a "Real" Horse unit in the British Army, as they have Corporal, Staff Corporal, Quartermaster Corporal, and even Company and Regimental Corporal-Major, all of which rank with [or above, since they're Household Cavalry] the Line NCO's.) If you hear of a Sergeant of Cavalry, well, he isn't REAL Cavalry, but from a one-time Dragoon regiment.
Since only the ranks, pay scales and names had changed (though the poor Dragoons were now encombered with rather long muskets to use for carbines as well, though otherwise they were equipped as Heavy Cavalry), there was a perceived need for, guess what, someone who would actually perform scouting and screening duties. Thus by the 1750's the Light Dragoons were invented, the first in British service being the 15th (King's) Light Dragoons. They were followed shortly by the 16th and 17th, and some of the earlier Dragoon regiments were later converted as well. On the Continent, the same need was felt, but rather than coverting Dragoons they formed new regiments based upon the rather flamboyant irregular troops employed by the Austrians in the form of the Hungarian Hussars. The duties were the same, the names and uniforms were, however, different. These Light Dragoons performed yeoman service in the American War/American Revolution, and were of course copied by the American forces in the form of such units on the Patriot side as the 1st-4th Light Dragoons, and on the Loyalist side by the British Legion Light Dragoons. They were armed with light carbines, swords and pistols, just like the "real" Cavalry of the English Civil War, sans some armour. But they were termed now "Light Dragoons".
By the Napoleonic Wars, the Hussar rage was riding quite high, and several of the British Light Dragoon regiments managed to, by one means or another, get themselves renamed "Hussars". Some (like the afore-mentioned 15th) were still Light Dragoons, but added Hussars to their name, as in "15th (King's) Light Dragoons (Hussars)". When the War of 1812 erupted between the US and Britain, the US was, of course, sans any Cavalry of any meaningful kind, and had to raise most of them from scratch. They fell back upon the older scheme of Light Dragoons, but for Volunteers, often as not the horsemen were rather termed "Mounted Rifles", as they were expected to do exactly what Dragoons had originally been formed to do: ride into battle, dismount and then fight on foot, in this case as Light Infantry/Rifles. One such unit, Richard Mentor Johnson's Kentucky Regiment of Mounted Rifles did a stellar job as such. However at the Battle of the Thames in 1813, one squadron of the Kentucky Mounted Rifles under Johnson's brother James did the standard switch: they remained mounted, and performed a charge against the 41st Foot and scattered them. The most interesting part of this was that tactically it was brilliant, as the 41st Foot was expecting them to dismount since they had no sabers, and was thus arrayed in skirmish order. James Johnson on the other hand ordered his men to "Draw Tomahawks" and charged them with tomahawks in hand, riding over them and smashing them, winning the battle.