If you have defeated the enemy either in the first round or subsequent rounds, you are allowed to "Fall Back". This is the correct term in the game for rallying. You roll 3d6 and are allowed to move anywhere from the lowest single dice roll up to the combined total of the 3 in any direction you wish. There are other conditions that apply to Falling Back but they are described in the rulebook.
So, taking the above into account, if your 'Fall Back' move allows you to contact an enemy character and there are no enemy units within 30cm of that character, he is dead - remove as if a casualty. If the character is a General, the battle is over.
Hope that helps.