DISUNION WAS PERHAPS the besetting sin of ancient Greece. The Greeks made many attempts and devised measures to remedy their weaknesses. Ineffective though their solutions were, it is difficult to see how more could have been achieved on a co-operative basis. In the fifth century B.c. after the Persian Wars the facts of inter-state diplomacy were comparatively simple, for Athens was the leading naval power and Sparta was the leading Peloponnesian and land power, and the other states tended to take their lead accordingly. In the fourth century inter-state relations became rather more complex, for the relative strengths of leading states had been decisively altered by the Peloponnesian War to the ultimate detriment of victor and vanquished alike. Athens had not only been beaten and deprived of her fleet, but the source of her power, the Delian League, had disappeared, and commercially Corinth and Rhodes had developed at her expense. Sparta in victory had over-extended her resources, lost her friends by arrogant behaviour, and damaged her social and military fabric. The decline of Athens and Sparta opened the way for Thebes, traditionally the second strongest power by land, to assume greater importance. Consequent upon the struggle between those three powers and the need for the one to redress the balance of power against the other two in combination Persia gained in influence, if only spasmodically, when called upon to intervene, and when she could be convinced of her own advantage. The great powers did not depend upon the inventions of weaponry and technology for their strength so much as upon military and naval training and tactics and, to an even greater extent, upon extension of alliances, for as often as not the military strength of a state depended upon the number of men or ships which it could contrive to muster from any source. Accordingly in the fourth century considerable attention was given to the making of treaties, the winning of allies, and the avoidance of losing friends, but, as we know, inter-state relations were characterized by chaos, disunion persisted, and the Greeks lost their liberty in the Macedonian victory in 338 at Chaeronea. For many the fourth century represents an era of decadence, since for them not only was the Greek political system so enervated as to pass under Macedonian control, but also in many fields the great artistic and cultural attainments of the past remained unsurpassed. The century was the so-called age of the individual, in which the great philosophers and political thinkers went unheeded. With hindsight it is possible for