Alexander the Great's conquest of the Persian Empire is significant not merely for its scale, but for the political form it encountered. Alexander conquered Asia in a few years and died before he had fully entered into possession of it, yet the territory did not immediately revolt. The durability of the conquest is explained by the structure of the kingdom he defeated: once Darius III had been overthrown and his line removed, no rival hereditary power remained except the ambitions and jealousies of Alexander's own successors.

Background and Political Structure

The conquest is introduced as a test of the general difficulty of holding newly acquired states. Alexander the Great had achieved the conquest of Asia rapidly, and his death before consolidation might reasonably have been expected to release a general uprising. Instead, the successors retained the country with no fundamental difficulty created by the population itself. The disorders that followed arose from their own rivalry rather than from a successful national revolt.

The explanation rests on a distinction between two forms of monarchy. In one, a sole prince governs while all other officials serve by his favor as ministers; in the other, the prince is surrounded by barons whose rank rests on ancient blood, whose territories and subjects are their own, and who are naturally loved by those subjects. A centralized monarchy gives the sovereign more complete authority because subordinate officials possess no independent personal claim on popular loyalty.

Course and Immediate Result

The kingdom of Darius III is treated as resembling the centralized model. Alexander therefore had first to defeat Darius III completely and strip him of his dominions. Once that defeat had occurred and Darius III had died, the political conditions that might have sustained organized resistance disappeared. The conquered population had no comparable network of hereditary lords through which a new invasion or rebellion could readily be organized.

The conquest thus depended on more than Alexander's military ability. Its result was shaped by the relation between the conqueror and the institutions of the conquered state. The destruction of the ruling line removed the principal source of alternative authority, while the centralized administration left no independent baronial class able to convert local discontent into a coordinated challenge.

Comparison with Other Conquests

The contrast is drawn with kingdoms resembling France, where powerful nobles can invite an invader, open the way into the country, and later lead renewed movements against the conqueror. In such states, destroying the ruling family's line is insufficient because other lords survive. A conqueror must either satisfy or eliminate them, and failure on either front can cause the newly acquired state to be lost when circumstances permit.

The same distinction explains why Alexander the Great could secure Asia more readily than Pyrrhus and many other conquerors could preserve their acquisitions. The difference did not necessarily lie in the relative merit of the conquerors. It lay in the different political characters of the states they attempted to hold. Alexander inherited a conquest whose centralized structure favored continuity; Pyrrhus faced acquisitions whose internal organization made lasting possession more difficult.

The comparison also reaches beyond the Persian Empire. The repeated risings of Spain, Gaul, and Greece against the Romans are attributed to the many small principalities formerly composing those provinces. Rome could not regard its authority as secure while the memory of those old rulers remained politically active. Only after the long duration and authority of Roman rule had erased that memory did the provinces become securely attached, ultimately recognizing no lords other than the Romans after the old ruling lines had disappeared.

Succession and Political Significance

The successors of Alexander the Great could have enjoyed Asia undisturbed had they remained united. Their failure to do so turned the principal danger inward: the conquest was not undone by a popular revolt but weakened by the ambition and mutual jealousy of the new rulers. The event therefore separates the problem of acquiring a state from the problem of preserving it after succession.

Its larger significance lies in the argument that conquest cannot be judged apart from the constitutional form of the conquered territory. A centralized kingdom may fall decisively with its sovereign and ruling line, whereas a composite order of hereditary powers can survive the fall of a single prince and continue to generate resistance. The conquest of the Persian Empire is consequently used as a political model: its apparent improbability after Alexander's death becomes evidence that the institutions of a state determine the ease or difficulty of imperial succession.