Archidamus II was a king of Sparta who reigned from approximately 476 BC to 427 BC. He was of the Eurypontid dynasty. His father was Zeuxidamus (called Cyniscus by many Spartans), who died before his father, Leotychidas, after having his son, Archidamus.
Leotychides, when Zeuxidamus was taken from him, married a second wife, named Eurydame, the sister of Menius and daughter of Diactorides. By her he had no male offspring, only a daughter called Lampito, whom he gave in marriage to his grandson Archidamus. He ascended the throne after his grandfather, Leotychidas II, was banished around 476 BC after being accused of bribery.
Archidamus was one of the kings of Sparta in the years preceding the Peloponnesian War. His coolness and presence of mind are said to have saved the Spartan state from destruction on the occasion of the great earthquake of 464 BC, but this story must be regarded as at least doubtful.
In 446 BC he agreed with Pericles on the Thirty Years' Peace between Athens and Sparta, bringing an end to the First Peloponnesian War, which had been raging since c. 460 BC.
During the negotiations that preceded the Peloponnesian War, he did his best to prevent, or at least to postpone, the inevitable struggle, but was overruled by the war party. He invaded Attica at the head of the Peloponnesian forces in the summers of 431, 430 and 428, and in 429 conducted operations against Plataea. He died probably in 427 BC, certainly before the summer of 426 BC, when we find his son Agis II on the throne.
(According to Thucydides in speeches attributed to Archidamus at the famous Debate at Sparta in 432 BC). These quotes are according to the copy of Thucydides edited by Paul Woodruff, "Thucydides on Justice Power and Human Nature"
"If we begin the war in haste, we'll have many delays before we end it, owing to our lack of preparation."
"We should not build our hopes on the belief that they will make mistakes, but on our own careful foresight. And we should not think there is much difference between one man and another, except that the winner will be the one whose education was the most severe."