A bridge, even a small one, needs more explosives than one man can carry. More some time is necessary to plant the charges and rigged them. That was not envisaged, in the scenario, since in CMFB bridges can not be blow up. The message, therefore comes to warn that the bridge is still up and to be prepared to it's use by the attacking forces. That is the way I felt it should be done, making the the scenario. Anyway at the time many units were having just the time to save their life facing a sudden and unexpected strong and wide attack.