How Common Were the Battles in the Middle Ages?

In Mediaeval armies, the combat units are generally called battles. And then you'r also grouping s together into a smaller, sort of squad size unit called a conroy. The stratification in ability and willingness to fight for these armies was really enormous. So how common were pitched field battles? When did this windid it comfl circle from the professional armies of the roman era back again to professional armies? Owhen when did they re emerge?