For France's army of the period of Jean Martinet (d1672) in the Early modern, how and why were cavalry used instead of infantry?
In European warfare the default company is the infantry company. This may be of varying grades of weight from royal guards through militia. But regardless of grade the infantry face the campaign and engagement in a common form. ^1^
In contrast cavalry squadrons face the strategy of campaign and the tactics of engagement quite differently from infantry. ^1^
How and why were cavalry employed differently to infantry?
The ideal answer will cover differential strategic mobility, independent march columns, screening scouting and anti-civilian actions; social policing and class; tactical mobility, manoeuvre, shock, lance armour and sword; and, cost of mobilisation, training and deployment.
^1^ with the exception of the dragoons