Book V:  After the armistice is concluded, Cleon, emboldened by his success in Pylos, leads an expedition through Thrace to Torone where he takes Torone, destroying some of Brasidas’ fortifications.  He makes Eion his base and Brasidas makes Amphipolis his, whereupon Cleon attacks, however in his delusions of grandeur he misjudges his ability, and tries to retreat too late.  In the fighting, Cleon is killed but his nemesis, Brasidas, is also fatally wounded.

Argos from Mycene (1884) Edward Lear source ArtUK

Both sides are eager for peace now, Athens suffering heavy losses, no longer certain of her strength in arms and worried about Sparta taking advantage of her weakness, and Sparta concerned about the devastation of their lands, deserting Helots, the return of the prisoners at Pylos to their important families, the possibility of civil war, their expiring thirty-year truce with Argos, and Peloponnesian cities intending to go over to the enemy.  Negotiations ensue with new leaders, Pleistoanax, son of Pausanias for Sparta and Nicias for Athens, each with their own agendas and with an idealistic view that peace would bring all things good with no repercussions from the war.  The peace treaty is then agreed upon.  Allies of Sparta refuse to accept the treaty, whereupon Sparta forms a fifty-year alliance with Athens, hoping this will dissuade aggression from Argos.  This happens in the winter of the tenth year of the war. Yet as time passes, the two powers begin to suspect each other, as both neglect to act on some of the conditions of the treaty, Sparta dragging her heels the most and being the whiniest.  Thucydides claims this was not a bonafide peace treaty but merely a ceasing of hostility in a war that continued.  

Near Athens (1863-65) Harry John Johnson source ArtUK

With the Corinthians once again causing trouble, they attempt to persuade Argos to go against Sparta.  Other states, uneasy with the treaty between the two major players, consider an alliance with the Argives.  More small invasions continue as does political plotting.  The Argives attempt to elicit a treaty with Sparta but changes its mind and makes one with Athens.  Alcibiades opposes Athens’ treaty with Sparta and Nicias pushes for its fulfillment while attempting to delay their treaty with the Argives, however he fails and the treaty is made, yet even so, the Athens and Sparta alliance continues.  The Spartans surround Argive forces, yet a truce is called by their leaders, Agis king of Sparta (remember the Spartan dual-king thing) and the Argive, Thrasylus.  The people on each side are furious at the undemocratic decision, each thinking they could have won; Thrasylus is stoned and has to flee to an altar to save his life and Agis nearly loses his home and is fined.  Instead, they enact a law, giving Agis ten counsellors and he is unable to make a decision without them.  

More fighting between Sparta and her allies and the Argives and her allies, then the Argives make an alliance with Sparta.  With infighting in Argos, the Argives change their minds again and reforge ties with Athens.Athens launches an expedition against Melos and after persuasive arguments, finally kills the men, sells the women and children as slaves, and settles Melos itself.

 

The bay of Milos source Wikipedia