Plutarch Pyrrhus 27

[1] After this, he marched down against the city of Sparta. Cleonymus urged him to make the assault as soon as he arrived, but Pyrrhus was afraid, as we are told, that his soldiers would plunder the city if they fell upon it at night, and therefore restrained them, saying that they would accomplish just as much by day. For there were but few men in the city, and they were unprepared, owing to the suddenness of the peril; and Areus was not at home, but in Crete, whither he was bringing military aid for the Gortynians. And this, indeed, more than anything else, proved the salvation of the city, which its weakness and lack of defenders caused to be despised.

[2] For Pyrrhus, thinking that no one would give him battle, bivouacked for the night, and the friends and Helot slaves of Cleonymus adorned and furnished his house in the expectation that Pyrrhus would take supper there with its owner.
  When night had come, the Lacedaemonians at first took counsel to send their women off to Crete, but the women were opposed to this; and Archidamia came with a sword in her hand to the senators and upbraided them in behalf of the women for thinking it meet that they should live after Sparta had perished.

[3] Next, it was decided to run a trench parallel with the camp of the enemy, and at either end of it to set their waggons, sinking them to the wheel-hubs in the ground, in order that, thus firmly planted, they might impede the advance of the elephants. When they began to carry out this project, there came to them the women and maidens, some of them in their robes, with tunics girt close, and others in their tunics only, to help the elderly men in the work.

[4] The men who were going to do the fighting the women ordered to keep quiet, and assuming their share of the task they completed with their own hands a third of the trench. The width of the trench was six cubits, its depth four, and its length eight hundred feet, according to Phylarchus; according to Hieronymus, less than this.

[5] When day came and the enemy were putting themselves in motion, these women handed the young men their armour, put the trench in their charge, and told them to guard and defend it, assured that it was sweet to conquer before the eyes of their fatherland, and glorious to die in the arms of their mothers and wives, after a fall that was worthy of Sparta. As for Chilonis, she withdrew from the rest, and kept a halter about her neck, that she might not come into the power of Cleonymus if the city were taken.