"The Clouds" represents a departure from the main themes of Aristophanes' early plays – Athenian politics, the Peloponnesian War and the need for peace with Sparta. The Spartans had recently stopped their annual invasions of Attica after the Athenians had taken Spartan hostages in the Battle of Sphacteria in 425 and this, coupled with a defeat suffered by the Athenians at the Battle of Delium in 424, had provided the right conditions for a truce. Thus the original production of "The Clouds" in 423 BC came at a time when Athens was looking forward to a period of peace. Cleon, the populist leader of the pro-war faction in Athens, was a target in all Aristophanes' early plays and his attempts to prosecute Aristophanes for slander in 426 had merely added fuel to the fire. Aristophanes however had singled Cleon out for special treatment in his previous play "The Knights" in 424 and there are relatively few references to him in "The Clouds".