The Causes of the Peloponnesian War: Part 3 – The Megarian Decree

As we have previously discussed, there were three suggested reasons from our ancient sources of the spark for the outbreak of the War. The Megarian Decree was the final spark that ignited the 27 year long struggle for dominance between Athens and her empire, and the Spartans and her allies. Thucydides glosses over the Decrees, and we can understand this as he was an Athenian citizen and inclined to see Athens as the victim in the struggle. However, The Decrees formed a major part of the outbreak of major hostilities and deserves a post devoted solely to it.
The Megarian Decree was a series of 4 decrees (questionably four…but for the sake of the blog we will go with the idea that there was four) were designed to break Megara through economic isolation. Megara was a city state situated on Just to the East of the Peloponnesian Isthmus and was a member of the Spartan Peloponnesian League. PeloponnesusCities

The reason for the Decree was accordingly due to the cultivating of sacred Athenian land and the killing of an Athenian herald. There is little evidence for this in the sources that we have available, and the Decree itself reduces the belief that this was the reason. All Megarian citizens were excluded from trade within the Athenian Empire, and if it were down to the cultivating of sacred land, it would seem weird to have the merchants and other citizens of Megara punished rather than merely the Megarian agriculturalists.
After the war over Corcyra and the subsequent treatments of Potidaea and Aegina, the Corinthians were on bad terms with the Athenians and Megarian ships had taken part on the Corinthian side at the Battle of Sybota. Jona Lendering argues that the Megarian Decrees were an attempt to isolate Corinth further by imposing sanctions on cities that supported the Corinthian cause. The Megarians complained to Sparta, her hegemonic power, and subsequently saw the Spartans threaten war unless the Decrees were revoked. The Idea that the Spartans were ordering the Athenians to do something, rather than take it to arbitration under the terms iof the treaty of 446 meant that the Hawkish faction in Athens were able to take the ascendancy. Pericles (the greatest of the Athenian Democrats in this period) believed he could isolate Corinth, but was mistaken in his belief of the Spartan reaction. The rejection of the demand to revoke the Decree gave the Spartans justification for war.

Further Reading:

Jona Lendering, Megarian Decree

Terry Buckley, Aspects of Greek History, Chapter 17

Thucydides, History of the Peloponnesian War, Chapter 1

Robert J Bonner, ‘The Megarian Decrees’, Classical Philology, Vol. 16, No. 3 (JUl., 1921, pp238-245