If a pursuing unit makes contact with an enemy unit that is not fleeing, the units become engaged in combat. If the enemy unit was engaged in combat at the start of this phase, and if that combat has not yet been fought, the pursuing unit will fight again when that combat is fought (and counts as having charged). However, it cannot pursue again this turn. Instead, it will automatically restrain and reform with no Restraint test required.
Otherwise, the units become locked in place until the next player's turn when they will fight a round of combat. During the next turn, the pursuing unit counts as having charged.