The want of enthusiasm on the part of the Spartan king, his multiplied delays, first at the isthmus, next in the march, and lastly before Œnoe, were all offensive to the fiery impatience of the army, who were loud in their murmurs against him. He acted upon the calculation already laid down in his discourse at Sparta—that the highly cultivated soil of Attica was to be looked upon as a hostage for the pacific dispositions of the Athenians, who would be more likely to yield when devastation, though not yet inflicted, was nevertheless impending and at their doors. In this point of view, a little delay at the border was no disadvantage; and perhaps the partisans of peace at Athens may have encouraged him to hope that it would enable them to prevail.
After having spent several days before Œnoe without either taking the fort or receiving any message from the Athenians, Archidamus marched onward to Eleusis and the Thriasian plain—about the middle of June, eighty days after the surprise of Platæa. His army was of irresistible force, not less than sixty thousand hoplites, according to the statement of Plutarch, or of one hundred thousand, according to others. Considering the number of constituent allies, the strong feeling by which they were prompted, and the shortness of the expedition combined with the chance of plunder, even the largest of these two numbers is not incredibly great, if we take it to include not hoplites only, but cavalry and light armed also. But as Thucydides, though comparatively full in his account of this march, has stated no general total, we may presume that he had heard none upon which he could rely.
As the Athenians had made no movement towards peace, Archidamus anticipated that they would come forth to meet him in the fertile plain of Eleusis and Thria, which was the first portion of territory that he sat down to ravage. Yet no Athenian force appeared to oppose him, except a detachment of cavalry, who were repulsed in a skirmish near the small lakes called Rheiti. Having laid waste this plain without any serious opposition, Archidamus did not think fit to pursue the straight road which from Thria conducted directly to Athens across the ridge of Mount Ægaleos, but turned off to the eastward, leaving that mountain on his right hand until he came to Cropia, where he crossed a portion of the line of Ægaleos over to Acharnæ.
He was here about seven miles from Athens, on a declivity sloping down into the plain which stretches westerly and northwesterly from Athens, and visible from the city walls; and here he encamped, keeping his army in perfect order for battle, but at the same time intending to damage and ruin the place and its neighbourhood. Acharnæ was the largest and most populous of all the demes in Attica, furnishing no less than three thousand hoplites to the national line, and flourishing as well by its corn, vines, and olives, as by its peculiar abundance of charcoal burning from the forests of ilex on the neighbouring hills. Moreover, if we are to believe Aristophanes, the Acharnian proprietors were not merely sturdy “hearts of oak,” but peculiarly vehement and irritable. It illustrates the condition of a Grecian territory under invasion, when we find this great deme, which could not have contained less than twelve thousand free inhabitants of both sexes and all ages, with at least an equal number of slaves, completely deserted. Archidamus calculated that when the Athenians actually saw his troops so close to their city, carrying fire and sword over their wealthiest canton, their indignation would become uncontrollable, and they would march out forthwith to battle. The Acharnian proprietors especially (he thought) would be foremost in inflaming this temper, and insisting upon protection to their own properties—or if the remaining citizens refused to march out along with them, they would, after having been thus left undefended to ruin, become discontented and indifferent to the general weal.