That was a real fowl defeat.

Basically at one time a Gaulic chieftain attempted to sack Rome. Rome was under siege for a while. One night the chieftain decided to scale the wall and silently sneak past the guards and their dogs. They did well until the geese caught wind and started honking and attacking the intruders. This essentially saved Rome from being totally destroyed in it's earlier times. This is why geese were largely revered in the roman times. This also led to a yearly festival in which Romans crucified dogs due to their inability to detect the Gaullic invades all that time ago.

@metalman thank you!

The Canadian geese would have sacked both groups and made nests in their corpses