Each character, lord or hero, takes up a certain space on the campain map. In order to not stack units on top of each other there is a collision box around each character. If a character moves close to a second character, he uses about 99% of his moveme and 1% will be removed due to the character beeing blocked by the second character.

If the second character moves 1% forward, the first character can follow up the second character in his footsteps by bumping into the first character collision box. Since the 1% gets subtracted when the first character bumpes into the second character, the first character will not use up any movement.

This is cumulative. If the second character keeps walking forward and the first character following in his footsteps, the first character will not use up any movement range. This will work until the second character run out of movement range.

This can also be addiditonally extended by the second character beeing a lord and carrying heroes. One of the heroes can be detached and the whole process can start a new.

You can also make a snail trail of lord and heros whereby only the first one in the row uses up movement and the following characters dont.