The first cuirassiers of the late 1500s were the direct descendants of the medieval men at arms and were not that different in appearance either, though their armour was considerably less heavy than their predescesors. As, heavy cavalry the charge was as always the key strategy but as infantry weapons modernised it was soon realised that the heavy armour served little purpose and was restrictive when using the new weapon of choice, the pistol!
In the 17th century conflicts such as the English Civil War and Thirty Years War cavalry armed themselves with multiple pairs of pistols (a weapon specifically developed for use by cavalry) as well as the traditional sabres, this meant that the horsemen didn't have to bother reloading their weapons, which is difficult enough to do from a horse even without armour. The addition of pistols meant that cavalry could carry more force on the charge and though they attempted a variety of obscure firing tactics, the cuirassiers were still very much a blunt tool to batter the enemy with.
The Cuirassiers of the 1700s were even further simplified, generally they wore only the cuirass of their name sake and an iron skullcap hidden beneath an elegant tricorne. With the advent of flintlock musketry the cuirass started to decline in use and some armies, including Britain removed the cuirass from service. The cuirassiers as a group had begun to change, no longer were they the sons of nobility instead they were required to be the tallest and strongest me in the cavalry regardless of social status. Though shock cavalry charges often won the day, the allied infantry attack against the famous French cavalry at Minden and the square formation revealed that with modern tactics and careful strategy even the feared cuirassiers could be beaten back. Though many nations still used the cuirassiers into the 19th century, the first signs of weakness were showing for the revered cuirassiers and indeed most cavalry, it would not be long till they were rendered obsolete.
Though the majority of armies fielded them in name in the early 1800s, due to financial difficulties many armies tried to do cuirassiers on the cheap, the Prussian Cuirassiers wore no cuirass and the Austrians only wore the front half, which was a disaster when they inevitably retreated. Cuirassiers from all nations still fought effectively and it was an awe inspiring sight to see the French and allied and the Russian cuirassiers clashing at Borodino. Cuirassiers or equivalent life guards were still a feature of most European armies throughout the rest of the 19th century and even the once forward thinking British still practiced square formations till the turn of the century.
The last blast of the trumpet for the cuirassiers like most cavalry came in the first world war, despite their brown cloth covering to hide the shine of their breastplates the French cuirassiers were extremely ineffective and suffered huge losses, cavalry had been beaten back for a final time, not with square formations and flintlock musketry but with barbed wire and machine gun fire.
Some countries still have cuirassiers for ceremonial purposes but its not exactly the real deal.
Thanks for reading, this was originally posted on my blog http://carausiuscreative.blogspot.co.uk/