When we think about warfare in the age of Louis XIV we tend to think of it as an age before the age of the skirmisher - for that was surely a product of the Age of Reason later on but this was not the case as George Satterfield proves in his Princes Posts and Partisans which is up on Google books for previewing and I heartily recommend it. The blurb reads; This volume explores French partisan warfare in the Spanish Netherlands during the Dutch War (1672-78). It considers such practices as contributions, fire-raids, and blockades before sieges. The author relies extensively on archival sources, and in many cases explores events that have been passed over by similar studies. Louis XIV and his generals used partisan warfare to fit a strategy of exhaustion to ensure territorial conquest. The French army's reliance on partisan warfare reveals the limitations of the war-making potential of Louis XIV's state; at the same time it leads to the emergence of a more modern practice of military operations to pursue theater-strategic objectives.
Armies had supply lines that were vulnerable to attack and harassment from the fringes was a feature of the period. If you downloaded Richard Kane's A New System of Military Discipline there is a piece in there that reads:
And though we have got clear of the Horse, yet we must still be on our guard against an ambuscade. Wherefore, we should be much more careful in marching through these grounds than over the plain. And though it may seem impossible that a sufficient body of Foot could be sent from the enemy’s frontiers to waylay us, yet as they always have a number of partisan parties abroad who may hear of our march and so draw together and lie hid in some close cover; and though they durst not openly attempt us, yet if they find us on a careless march, may throw in among us, which would certainly put us under great confusion. And ‘tis hard to say what may be the consequence, for I have known some of these impudent fellows that have lain hid in a wood, fire upon the skirt of our grand army as we have been on the march. Wherefore I say, great care must be taken in marching through inclosed grounds where both the advance and rear guards ought to be more circumspect in looking about them, and send men off on every side to inspect into all suspected covers.