The support bridge is a way to organize your defenses, the system calculates the amount of incoming troops and checks if at the time of particular battle round, will there be over 100(castle)/500(fortress) units on defender side. Should this be the case the system assumes that if the attacker side also reaches this minimum requirement, the battle round will be successfully defended and a next one will take place. The user can manually edit rounds if he thinks that he will have recruited troops up until that point etc. Using the orange icon can be used for showing the other support bridge participants that the battle round will be taken care of or not.
GREEN = All good this battle round is covered
ORANGE = Troops are being made to cover this battle round or support is on its way
RED = This round is not covered i need support