If the enemy has fled out of reach, or if you have estimated your charge incorrectly, your troops might not be able to move far enough to reach their target. If this is the case, the charge has failed.
If a charge fails, the unit is moved at its normal Move rate rather than double speed. The unit is moved directly towards the intended target as if it were charging, but halts once it has covered its normal Move distance. This represents when troops have begun to charge before realising it is impossible to reach their enemy; consequently their movement peters out as they lose impetus and enthusiasm (See Diagram 21.1 - A Failed Charge).
A unit that fails its charge cannot shoot with missile weapons that turn, though Wizards may cast spells.