History of the Peloponnesian War

Those, too, who were familiar with it, recalled that other oracle given to the Lacedaemonians, when, in answer to their inquiry whether they should go to war, the god responded that if they "warred with all their might victory would be theirs," adding that he himself would assist them.i Now so far as the oracle is concerned, they surmised that what was then happening was its fulfilment, for the plague broke out immediately after the Peloponnesians had invaded Attica;

and though it did not enter the Peloponnesus to any extent, it devastated Athens most of all, and next to Athens the places which had the densest population. So much for the history of the plague.