New idea for unit special ability

[Mik1984]

What if retreat was possible only to an adjacent tile occupied by units of the retreating civ? If retreat were possible to multiple adjacent and occupied tiles, then the unit would always retreat to the most heavily occupied tile, i.e. the tile with the most units. If there are no adjacent tiles occupied by retreating civ, then the unit cannot retreat and is destroyed. This rule would encourage the use of formations to support units with retreat options.

That could be good, for civ5. I wouldn't even try to rescue civ4 in this area.