At the start of your Movement phase, the first thing you must do is declare which units (if any) will charge. Units are not normally obliged to charge unless a special rule states otherwise.

Charging is the only way for a unit to move itself into combat with the foe. If you want to engage an enemy in combat then you must charge them – you cannot simply move into combat without having first declared a charge.

To declare a charge you must indicate which of your units is charging, and which enemy unit it is going to charge. A charged unit is often referred to as the 'charge target'. When you declare a charge, one or more of the models in your unit must be able to draw a line of sight to the charge target, and the charge target must lie at least partially within the charging unit's front arc.

You are always allowed to measure the distance between your unit and the potential charge target before declaring the charge, and should take into account any terrain that might slow the unit down, as this might well affect your decision whether or not to declare a charge.

Charge movement is explained in The Charge Move section.