The chevau‑légers (light horse) made up the bulk of the French line cavalry. The name seems a misnomer, since the chevau‑légers were cuirassiers, not really "light cavalry," but it was a holdover from the 16th Century, when the chevau‑légers were indeed "light," at least compared to the more heavily armed and armored gendarmes whom they supported in combat.
Until 1635 the chevau‑légers were organized in companies, usually of 100 maîtres (since the troopers were gentlemen), commanded by a captain, who was assisted by a lieutenant and a cornet (i.e., a standard‑bearer). In 1634 alone, with war imminent, 91 100-man companies were formed (list in Choppin, 100).
On 16/26 May 1635 a royal ordinance prescribing the formation of cavalry regiments was promulgated. Initially, 12 French regiments were formed, and three foreign corps, which were already organized as regiments, were taken into French service. The French regiments were created by redesignating the 12 oldest companies of chevau‑légers, the "compagnies d'anciennes ordonnances," as regiments. All the captains of the old companies, save one, were named mestres de camp of the new regiments. The other companies, and there were a multitude of them, were assigned to one of the new regiments. The average regiment would appear to have had an assigned strength of 600 troopers in 6 companies, although some authors state that the regiments formed at this time had 12 companies.
The French regiments formed, with the dates of their disbandment shown in parentheses next to their names, were:
La Meilleraye (1661)
Le Ferron (1636)
Two of the foreign corps taken into French service at this time were units that had formerly served the Duke of Savoy. The other was the Franco‑German cavalry regiment of the remarkable French soldier‑adventurer Jean de Gassion. Gassion, who had served Gustavus Adolphus and Bernhard of Saxe‑Weimar as a cavalryman, commanded a regiment of 1,400 men, organized from 12 companies of horse and 2 companies of dragoons. All the horse were well‑mounted, with pot helm and cuirass.
It should be noted that this was a very large regiment by the standards of the time, and we may infer that Gassion had benefited from his position as a favorite of the Swedish king. In 1638, the regiment was with the army of Maréchal Chatillon; at that time it had a strength of 1,700 troopers in 16 companies (and Gassion had found a new patron in Richelieu).
The new regimental organization was meant to bring the cavalry more effectively under the control of the central government by diminishing the privileges of the captains, which had been much abused, and by diminishing too the number of units. However, it proved very difficult to persuade the heretofore independent captains to obey the new mestres de camp. For example, at the camp of Drouay in Picardy in 1636, an insubordinate captain quarreled violently with his mestre de camp Canillac in front of the troops. Swords were drawn, and it was only with difficulty that the Duke of Soissons was able to intervene to stop the fighting.
The recalcitrance of the captains forced the government to rethink its policy on regimenting the cavalry, and for a brief period, beginning in 1636, the ordinance was revoked and the companies were reconstituted. However, on 24 July 1638, the regimental organization was again adopted--this time for good. At this time there were 36 600-man regiments.
An ordinance of 24 February 1647 incorporated the foreign regiments into the French army, ending the exalted privileges of the Weimarian colonels. At that time there were 68 cavalry regiments, of which 12 were foreign.
In 1654, the strength of the company was fixed at 46 troopers, and that of the squadron at 96. Thus, a squadron formed for battle in three ranks would present a front of 30 files.