Plutarch Pyrrhus 12

[1] But now Lysimachus made his appearance, claimed that the overthrow of Demetrius had been the joint work of both, and demanded a division of the kingdom. So Pyrrhus, who did not yet feel entire confidence in the Macedonians, but was still doubtful about them, accepted the proposition of Lysimachus, and they divided the cities and the territory with one another.

[2] This availed for the present, and prevented war between them, but shortly afterward they perceived that the distribution which they had made did not put an end to their enmity, but gave occasion for complaints and quarrels. For how men to whose rapacity neither sea nor mountain nor uninhabitable desert sets a limit, men to whose inordinate desires the boundaries which separate Europe and Asia put no stop, can remain content with what they have and do one another no wrong when they are in close touch,

[3] it is impossible to say. Nay, they are perpetually at war, because plots and jealousies are parts of their natures, and they treat the two words, war and peace, like current coins, using whichever happens to be for their advantage, regardless of justice; for surely they are better men when they wage war openly than when they give the names of justice and friendship to the times of inactivity and leisure which interrupt their work of injustice.

[4] And Pyrrhus made this plain; for, setting himself to hinder the growing power of Demetrius, and trying to prevent its recovery, so to speak, from a serious illness, he went to the help of the Greeks and entered Athens. Here he went up to the acropolis and sacrificed to the goddess, then came down again on the same day, and told the people he was well pleased with the confidence and goodwill which they had shown him, but that in future, if they were wise, they would not admit any one of the kings into their city nor open their gates to him.

[5] After this, he actually made peace with Demetrius, but in a little while, when Demetrius had set out for Asia, he once more took the advice of Lysimachus and tried to bring Thessaly to revolt, besides waging war upon the garrisons of Demetrius in the Greek cities. For he found that the Macedonians were better disposed when they were on a campaign than when they were unoccupied, and he himself was by nature entirely averse to keeping quiet.
  But at last, after Demetrius had been wholly overthrown in Syria, ¹ Lysimachus, who now felt himself secure, and had nothing on his hands, at once set out against Pyrrhus.

[6] Pyrrhus was in camp at Edessa, where Lysimachus fell upon his provision trains and mastered them, thus bringing him to straits; then, by letters and conferences he corrupted the leading Macedonians, upbraiding them because they had chosen as lord and master a man who was a foreigner, whose ancestors had always been subject to Macedonia, and were thrusting the friends and familiars of Alexander out of the country.

[7] After many had thus been won over, Pyrrhus took alarm and departed with his Epeirots and allied forces, thus losing Macedonia precisely as he got it. ² Whence we see that kings have no reason to find fault with popular bodies for changing sides as suits their interests; for in doing this they are but imitating the kings themselves, who are their teachers in unfaithfulness and treachery, and think him most advantaged who least observes justice.