While you can argue whether the appropriate appellation would be "skirmish," "engagement," "battle," or whatever, the number of combatants does not necessarily have any influence as to the decisive nature of the result. The Plains of Abraham featured total force committments that wouldn't have been classed as much above a "rear guard" for a contintental army, yet the impact was decisive. Clive commanded only 500 or so at the siege of Arcot, but when the dust finally settled, Clive had put a new nawab on the throne.