Players will sometimes find that the movement of troops results in the tabletop becoming quite crowded, especially when several different units are engaged in close combat. It is obviously important to establish what units are actually fighting and which are close by but not engaged, perhaps merely passing by.
For this reason, opposing troops are kept at least 1" apart when they are not fighting. Models which would otherwise approach to within 1" of an enemy without engaging them are simply halted 1" away. Remember that in normal circumstances units may only engage in close combat by means of a charge. However, during charge moves a charging unit may approach within 1" of any enemy (not only the ones they are charging).