Numbering can be a bit confusing. There were seven Dragoon Guards regiments numbered from 1 to 7 and there were six Dragoons Regiments which were classified as heavy were numbered from 1 - 6. Dragoon Regiments with numbers over 6 were classified as light regiments.

The Light Cavalry had a slightly different role to the heavy regiments. Much of what they did was in the role skirmishing, communications between army encampments. They provided a vital communication, listening and watching role. They proved pivotal in roles such as retreats where they could hold off the enemy giving their army valuable time to regroup or cover distance before galloping back. The light regiments of the British Army were Dragoon Regiments numbered from 7 to 25. In 1806 4 of these Dragoon regiments were changed to 'Hussar' regiments - the 7th, 11th, 15th and 18th. This was really only a change in uniform.

Cavalry regimental structure was simple. A battalion had ten troops of around 90 men. These troops paired off to make 5 squadrons. It was usual for a battalion to send four squadron's into the field and leave one squadron at home. This was like a bank of potential recruits meaning the natural attrition of war and sickness could in part be countered by having replacements trained and ready at hand.

definitions
Dragoon - A name given to mounted soldiers, said to have originated from the French 'Dragon' or short musket used by them and so called because of the shape of the cocking piece.
Hussar - A word from 15th century Hungary meaning 'one in twenty'. This relates to the conscripting of one man in twenty from every village.
Other terms for cavalry you may have heard are the French Cuirassiers, they were the only armoured cavalry of this period.

As a general grouping Heavy cavalry are termed as Cuirassiers and Heavy dragoons. Lancers, Hussars, and Light Dragoons were light cavalry. The Lancers were named for the weapon they carried which was - unsurprisingly - a longish lance, which was about the only effective weapon for poking at the enemy when they were formed in their 'squares.' Britain had no Cavalry Lancers at this time.

It must have been impressive and frightening watching the cavalry approach, they increased in speed and generally only galloped for the last 50 yards so the horses wouldn't be blown before getting to the enemy's line. When meeting the enemy cavalry unit it was standard to meet them at speed to - two lines of horses galloping towards one another!

Again, as with the cavalry, each regiment had a certain number of battalions, at least 2 per regiment and sometimes up to three or four.

Each battalion had ten companies of up to 100 men (see the glossary for more information .) The intention of having more than one battalion was that a regiment would keep one battalion at home and send the other one into the field. Again being able to send men to replace the ones killed, invalided or struck down by sickness.

In 1811 there were 46 battalions on the Peninsula, only 9 of these had more than 700 in active service, the rest had around 550 (that's almost half strength), one had 263.

Sometimes a Regiment's second battalion was called into service which was when problems really began to arise. A second battalion would be already reduced in strength having contributed to the strength of the first battalion so they were invariably much weaker.

As I have said each Battalion had ten companies. Two of these, the best two, were determined the right and left flanks for the battalion. The right flank company had once been issued with grenades and so were called the Grenadiers. The left company were called the 'light'. These two companies were vital. A battalion was most exposed on its flanks so it needed to have its most experienced men to protect them there.

And why the size of companies and the size of battalions? Well this was the age when communication was through drums and trumpet. This was deemed both the most manageable size for a group to be able to fight as a unit and still know what was happening. Larger than that and control could be lost. And manouvres as a cohesive unit were vital infantry battalions were only strong if they worked together and there were very specific drills that they were drilled in interminably. Learning them was the difference between life and death on the battle field. Although a packed unit was vulnerable to fire from artillery and muskets, as a group they could escape the every present problem or cavalry who easily picked off men in loose lines of infantry.