History of the Peloponnesian War

Now the Argives had from the first been aware of the preparations of the Lacedaemonians; and when they were on their march for the purpose of joining the rest at Phlius, then they also took the field. They were reinforced by the Mantineans with their allies, and by three thousand heavy-armed of the Eleans.

And as they advanced, they met the Lacedaemonians at Methydrium in Arcadia, and each army occupied a hill. The Argives then prepared to engage the Lacedaemonians, cut off as they were by themselves: but Agis broke up in the night, and eluding them, proceeded to the rest of the allies at Phlius.