History of the Peloponnesian War

For there were in the place some settlers from Argilus, an Andrian colony; these and some others were his accomplices in this intrigue, some instigated by Perdiccas, others by the Chalcidians.

But the chief plotters were the Argilians, who dwelt near by, were always suspected by the Athenians, and were secret enemies of the place; now that opportunity offered and Brasidas had come, they had some time before negotiated with their countrymen who resided in Amphipolis with a view to the surrender of the place. So at this time they received Brasidas into their town, revolted from the Athenians that same night, and before dawn brought his army down to the bridge over the river, which is some distance from the town and not connected with it by walls as now.

Brasidas easily forced the small guard stationed at the bridge, partly because there was treachery, partly because he had fallen upon them in stormy weather and unexpectedly; and as soon as he had crossed the bridge he was at once master of the property of the Amphipolitans outside the walls; for they had houses all over the neighbourhood.

His crossing had surprised the people inside the city, and of those outside many were captured, while others took refuge within the walls; hence the Amphipolitans were thrown into great confusion, especially as they were suspicious of each other.

Indeed the general impression was, it is said, that if Brasidas, instead of turning to pillage with his army, had decided to march straight against the city, he could have taken it.