The Dorians apparently displace the early inhabitants of Megara, a settlement on the Saronic Gulf within Attica and situated on the southern slopes of two hills that serve as the acropolises (citadels) of the ancient town.

Theagenes of Megara, who builds a fountain house (that can still be seen off the “Road of the Spring-House” in modern Megara), “slaughters the flocks of the rich” (an action incomprehensible without more background information than is available) and tries in about 632 to help his son-in-law Cylon to power at Athens.

The history of Megara after 630 BCE is largely that of its losing conflict with its powerful neighbor, Athens, to which ...

…like the Argives, the Megarians had also felt pressure from Corinth and turned to Athens.

This is the cause and beginning of the “violent hatred” between Corinth and Athens, which produces what modern scholars call the First Peloponnesian War (460-446).

Megara, quarreling with Spartan ally Corinth, has requested and received aid from the Athenians, who defeat the Corinthian fleet in 460 and, in 459, a Corinthian army sent to raid Megara.

…that of Megara, which had been forced to accept Athenian defensive assistance after 461 BCE.

…this pressure is felt in Corinth's own backyard, at Megara.

Athens passes a series of measures (the “Megarian decrees”) imposing an economic embargo on Megara for violations of sacred land.

The religious aspect of the offense is reflected in the exclusions imposed: like murderers, the Megarians are banned from the Athenian marketplace and the harbors in the Athenian empire.

However, there is no doubt that Athens causes and intends to cause economic hardship as well or that the decrees are the first move in securing Megara as a military asset.

…a morale-boosting raid on the Megarid (such raids will be repeated twice a year until 424); …

Athens mounts a vain attempt by the Athenian general Nicias to take Megara by military means in 427, then ...

Athens makes a serious and initially successful attempt, under Demosthenes, on Megara and its port, Nisaea, followed by …