Brasidas now marched against this town, starting from Arne in Chalcidice.
Arriving about dusk at Aulon and Bromiscus, where the lake of Bolbe runs into the sea, he supped there, and went on during the night.
The weather was stormy and it was snowing a little, which encouraged him to hurry on, in order, if possible, to take every one at Amphipolis by surprise, except the party who were to betray it.
The plot was carried on by some natives of Argilus, an Andrian colony, residing in Amphipolis, where they had also other accomplices gained over by Perdiccas or the Chalcidians.
But the most active in the matter were the inhabitants of Argilus itself, which is close by, who had always been suspected by the Athenians, and had had designs on the place.
These men now saw their opportunity arrive with Brasidas, and having for some time been in correspondence with their countrymen in Amphipolis for the betrayal of the town, at once received him into Argilus, and revolted from the Athenians, and that same night took him on to the bridge over the river;
where he found only a small guard to oppose him, the town being at some distance from the passage, and the walls not reaching down to it as at present.
This guard he easily drove in, partly through there being treason in their ranks, partly from the stormy state of the weather and the suddenness of his attack, and so got across the bridge, and immediately became master of all the property outside; the Amphipolitans having houses all over the quarter.