History of the Peloponnesian War
Thucydides
Thucydides. History of the Peloponnesian War. Crawley, Richard, translator. London and Toronto: J. M. Dent and Sons Ltd.; New York: E. P. Dutton and Co., 1914.
Later on, envoys arrived with messages from the Argives in the town and from the exiles, when the allies were also at Sparta; and after much had been said on both sides, the Lacedaemonians decided that the party in the town had done wrong, and resolved to march against Argos, but kept delaying and putting off the matter.
Meanwhile the commons at Argos, in fear of the Lacedaemonians, began again to court the Athenian alliance, which they were convinced would be of the greatest service to them; and accordingly proceeded to build long walls to the sea, in order that in case of a blockade by land, with the help of the Athenians they might have the advantage of importing what they wanted by sea.
Some of the cities in Peloponnese were also privy to the building of these walls; and the Argives with all their people, women and slaves not excepted, addressed themselves to the work, while carpenters and masons came to them from Athens.Summer was now over.
The winter following the Lacedaemonians, hearing of the walls that were building, marched against Argos with their allies, the Corinthians excepted, being also not without intelligence in the city itself; Agis, son of Archidamus, their king, was in command.