The system of checks, while it was effectual for the object at which it specially aimed, had one great disadvantage. It weakened the hands of authority in times of difficulty. When danger, internal or external, threatened, it was an evil that the powers of government should be divided, and the civil authority lodged in the hands of one officer, the military in those of another. Concentration of power is needed for rapid and decisive action, for unity of purpose, and secrecy both of plan and of execution. These considerations led to a modification of the original idea of satrapial government, which was adopted partially at first—in provinces especially exposed to danger, internal or external—but which ultimately became almost universal. The offices of satrap, or civil administrator, and commandant, or commander of the troops, were vested in the same person, who came in this way to have that full and complete authority which is possessed by Turkish pashas and modern Persian khans or beys—an authority practically uncontrolled. This system was advantageous for the defence of a province against foes; but it was dangerous to the stability of the Empire, since it led naturally to the occurrence of formidable rebellions.

Two minor points in the scheme of Darius remain to be noticed, before this account of his governmental system can be regarded as complete. These are his institution of posts, and his coinage of money.

In Darius’s idea of government was included rapidity of communication. Regarding it as of the utmost importance that the orders of the Court should be speedily transmitted to the provincial governors, and that their reports and those of the royal secretaries should be received without needless delay, he established along the lines of routes already existing between the chief cities of the Empire a number of post-houses, placed at regular intervals, according to the estimated capacity of a horse to gallop at his best speed without stopping. At each post-house were maintained, at the cost of the state, a number of couriers and several relays of horses. When a despatch was to be forwarded it was taken to the first post-house along the route, where a courier received it, and immediately mounting on horseback galloped with it to the next station. Here it was delivered to a new courier, who, mounted on a fresh horse, took it the next stage on its journey; and thus it passed from hand to hand till it reached its destination. According to Xenophon, the messengers travelled by night as well as by day; and the conveyance was so rapid that some even compared it to the flight of birds. Excellent inns or caravanserais were to be found at every station; bridges or ferries were established upon all the streams; guard-houses occurred here and there, and the whole route was kept secure from the brigands who infested the Empire. Ordinary travellers were glad to pursue so convenient a line of march; it does not appear, however, that they could obtain the use of post-horses even when the government was in no need of them. The coinage of Darius consisted, it is probable, both of a gold and silver issue. It is not perhaps altogether certain that he was the first king of Persia who coined money; but, if the term “daric” is really derived from his name, that alone would be a strong argument in favor of his claim to priority. In any case, it is indisputable that he was the first Persian king who coined on a large scale, and it is further certain that his gold coinage was regarded in later times as of peculiar value on account of its purity. His gold darics appear to have contained, on an average, not quite 124 grains of pure metal, which would make their value about twenty two shillings of our money. They were of the type usual at the time both in Lydia and in Greece—flattened lumps of metal, very thick in comparison with the size of their surface, irregular, and rudely stamped. The silver darics were similar in general character, but exceeded the gold in size. Their weight was from 224 to 230 grains, and they would thus have been worth not quite three shillings of our money. It does not appear that any other kinds of coins besides these were ever issued from the Persian mint. They must, therefore, it would seem, have satisfied the commercial needs of the people.

From this review of the governmental system of Darius we must now return to the actions of his later life. The history of an Oriental monarchy must always be composed mainly of a series of biographies; for, as the monarch is all in all in such communities, his sayings, doings, and character, not only determine, but constitute, the annals of the State. In the second period of his reign, that which followed on the time of trouble and disturbance, Darius (as has been already observed) appears to have pursued mainly the arts of peace. Bent on settling and consolidating his Empire, he set up everywhere the satrapial form of government, organized and established his posts, issued his coinage, watched over the administration of justice, and in various ways exhibited a love of order and method, and a genius for systematic arrangement. At the same time he devoted considerable attention to ornamental and architectural works, to sculpture, and to literary composition. He founded the royal palace at Susa, which was the main residence of the later kings. At Persepolis he certainly erected one very important building; and it is on the whole most probable that he designed—if he did not live to execute—the Chehl Minor itself—the chief of the magnificent structures upon the great central platform. The massive platform itself, with its grand and stately steps, is certainly of his erection, for it is inscribed with his name. He gave his works all the solidity and strength that is derivable from the use of huge blocks of a good hard material. He set the example of ornamenting the stepped approached to a palace with elaborate bas-reliefs. He designed and caused to be constructed in his own lifetime the rock-tomb at Nakhsh-i-Rustam, in which his remains were afterwards laid. The rock-sculpture at Behistun was also his work. In attention to the creation of permanent historical records he excelled all the Persian kings, both before him and after him. The great Inscription of Behistun has no parallel in ancient times for length, finish, and delicacy of execution, unless it be in Assyria or in Egypt. The only really historical inscription at Persepolis is one set up by Darius. He was the only Persian king, except perhaps one, who placed an inscription upon his tomb. The later monarchs in their records do little more than repeat certain religious phrases and certain forms of self-glorification which occur in the least remarkable inscriptions of their great predecessor. He alone oversteps those limits, and presents us with geographical notices and narratives of events profoundly interesting to the historian.

During this period of comparative peace, which may have extended from about B.C. 516 to B.C. 508 or 507, the general tranquillity was interrupted by at least one important expedition. The administrational merits of Darius are so great that they have obscured his military glories, and have sent him down to posterity with the character of an unwarlike monarch—if not a mere “peddler,” as his subjects said, yet, at any rate, a mere consolidator and arranger. But the son of Hystaspes was no carpet prince. He had not drawn the sword against his domestic foes to sheath it finally and forever when his triumph over them was completed. On the contrary, he regarded it as incumbent on him to carry on the aggressive policy of Cyrus and Cambyses, his great predecessors, and like them to extend in one direction or another the boundaries of the Empire. Perhaps he felt that aggression was the very law of the Empire’s being, since if the military spirit was once allowed to become extinct in the conquering nation, they would lose the sole guarantee of their supremacy. At any rate, whatever his motive, we find him, after he had snatched a brief interval of repose, engaging in great wars both towards his eastern and his western frontier—wars which in both instances had results of considerable importance.

The first grand expedition was towards the East. Cyrus, as we have seen, had extended the Persian sway over the mountains of Affghanistan and the highlands from which flow the tributaries of the Upper Indus. From these eminences the Persian garrisons looked down on a territory possessing every quality that could attract a powerful conqueror. Fertile, well-watered, rich in gold, peopled by an ingenious yet warlike race, which would add strength no less than wealth to its subjugators, the Punjab lay at the foot of the Sufeid Koh and Suliman ranges, inviting the attack of those who could swoop down when they pleased upon the low country. It was against this region that Darius directed his first great aggressive effort. Having explored the course of the Indus from Attock to the sea by means of boats, and obtained, we may suppose, in this way some knowledge of the country and its inhabitants, he led or sent an expedition into the tract, which in a short time succeeded in completely reducing it. The Punjab, and probably the whole valley of the Indus, was annexed, and remained subject till the later times of the Empire. The results of this conquest were the acquisition of a brave race, capable of making excellent soldiers, an enormous increase of the revenue, a sudden and vast influx of gold into Persia, which led probably to the introduction of the gold coinage, and the establishment of commercial relations with the natives, which issued in a regular trade carried on by coasting-vessels between the mouths of the Indus and the Persian Gulf.

The next important expedition—one probably of still greater magnitude—took exactly the opposite direction. The sea which bounded the Persian dominion to the west and the north-west narrowed in two places to dimensions not much exceeding those of of the greater Asiatic rivers. The eye which looked across the Thracian Bosphorus or the Hellespont seemed to itself to be merely contemplating the opposite bank of a pretty wide stream. Darius, consequently being master of Asia Minor, and separated by what seemed to him so poor a barrier from fertile tracts of vast and indeed indefinite extent, such as were nowhere else to be found on the borders of his empire, naturally turned his thoughts of conquest to this quarter. His immediate desire was, probably, to annex Thrace; but he may have already entertained wider views, and have looked to embracing in his dominions the lovely isles and coasts of Greece also, so making good the former threats of Cyrus. The story of the voyage and escape of Democedes, related by Herodotus with such amplitude of detail, and confirmed to some extent from other sources, cannot be a mere myth without historical foundation. Nor is it probable that the expedition was designed merely for the purpose of “indulging the exile with a short visit to his native country,” or of collecting “interesting information.” If by the king’s orders a vessel was fitted out at Sidon to explore the coasts of Greece under the guidance of Democedes, which proceeded as far as Crotona in Magna Grsecia, we may be tolerably sure that a political object lay at the bottom of the enterprise. It would have exactly the same aim and end as the eastern voyage of Scylax, and would be intended, like that, to pave the way for a conquest. Darius was therefore, it would seem, already contemplating the reduction of Greece Proper, and did not require to have it suggested to him by any special provocation. Mentally, or actually, surveying the map of the world, so far as it was known to him, he saw that in this direction only there was an attractive country readily accessible. Elsewhere his Empire abutted on seas, sandy deserts, or at best barren steppes; here, and here only, was there a rich prize close at hand and (as it seemed) only waiting to be grasped.

But if the aggressive force of Persia was to be turned in this direction, if the stream of conquest was to be set westward along the flanks of Rhodope and Haemus, it was essential to success, and even to safety, that the line of communication with Asia should remain intact. Now, there lay on the right flank of an army marching into Europe a vast and formidable power, known to be capable of great efforts, which, if allowed to feel itself secure from attack, might be expected at any time to step in, to break the line of communication between the east and west, and to bring the Persians who should be engaged in conquering Pseonia, Macedonia, and Greece, into imminent danger. It is greatly to the credit of Darius that he saw this peril—saw it and took effectual measures to guard against it. The Scythian expedition was no insane project of a frantic despot, burning for revenge, or ambitious of an impossible conquest. It has all the appearance of being a well-laid plan, conceived by a moderate and wise prince, for the furtherance of a great design, and the permanent advantage of his empire. The lord of South-Western Asia was well aware of the existence beyond his northern frontier of a standing menace to his power. A century had not sufficed to wipe out the recollection of that terrible time when Scythian hordes had carried desolation far and wide over the fairest of the regions that were now under the Persian dominion. What had occurred once might recur. Possibly, as a modern author suggests, “the remembrance of ancient injuries may have been revived by recent aggressions.” It was at any rate essential to strike terror into the hordes of the Steppe Region in order that Western Asia might attain a sense of security. It was still more essential to do so if the north-west was to become the scene of war, and the Persians were to make a vigorous effort to establish themselves permanently in Europe. Scythia, it must be remembered, reached to the banks of the Danube. An invader, who aspired to the conquest even of Thrace, was almost forced into collision with her next neighbor.

Darius, having determined on his course, prefaced his expedition by a raid, the object of which was undoubtedly to procure information. He ordered Ariaramnes, satrap of Cappadocia, to cross the Euxine with a small fleet, and, descending suddenly upon the Scythian coast, to carry off a number of prisoners. Ariaramnes executed the commission skilfully, and was so fortunate as to make prize of a native of high rank, the brother of a Scythian chief or king. From this person and his companions the Persian monarch was able to obtain all the information which he required. Thus enlightened, he proceeded to make his preparations. Collecting a fleet of 600 ships, chiefly from the Greeks of Asia, and an army estimated at from 700,000 to 800,000 men, which was made up of contingents from all the nations under his rule, he crossed the Bosphorus by a bridge of boats constructed by Mandrocles a Samian; marched through Thrace along the line of the Little Balkan, receiving the submission of the tribes as he went; crossed the Great Balkan; conquered the Getae, who dwelt between that range and the Danube; passed the Danube by a bridge, which the Ionian Greeks had made with their vessels just above the apex of the Delta; and so invaded Scythia. The natives had received intelligence of his approach, and had resolved not to risk a battle. They retired as he advanced, and endeavored to bring his army into difficulties by destroying the forage, driving off the cattle, and filling in the wells. But the commissariat of the Persians was, as usual, well arranged. Darius remained for more than two months in Scythia without incurring any important losses. He succeeded in parading before the eyes of the whole nation the immense military power of his empire. He no doubt inflicted considerable damage on the hordes, whose herds he must often have captured, and whose supplies of forage he curtailed. It is difficult to say how far he penetrated. Herodotus was informed that he marched east to the Tanais (Don), and thence north to the country of the Budini, where he burnt the staple of Gelonus, which cannot well have been below the fiftieth parallel, and was probably not far from Voronej. It is certainly astonishing that he should have ventured so far inland, and still more surprising that, having done so, he should have returned with his army well-nigh intact. But we can scarcely suppose the story that he destroyed the staple of the Greek trade a pure fiction. He would be glad to leave his mark in the country, and might make an extraordinary effort to reach the only town that was to be found in the whole steppe region. Having effected his purpose by its destruction, he would retire, falling back probably upon the coast, where he could obtain supplies from his fleet. It is beyond dispute that he returned with the bulk of his army, having suffered no loss but that of a few invalid troops whom he sacrificed. Attempts had been made during his absence to induce the Greeks, who guarded the bridge over the Danube, to break it, and so hinder his return; but they were unsuccessful. Darius recrossed the river after an interval of somewhat more than two months, victorious according to his own notions, and regarded himself as entitled thenceforth to enumerate among the subject races of his empire “the Scyths beyond the sea.” On his return march through Thrace, he met, apparently, with no opposition. Before passing the Bosphorus, he gave a commission to one of his generals, a certain Megabazus, to complete the reduction of Thrace, and assigned him for the purpose a body of 80,000 men, who remained in Europe while Darius and the rest of his army crossed into Asia.

Megabazus appears to have been fully worthy of the trust reposed in him. In a single campaign (B.C. 506) he overran and subjugated the entire tract between the Propontis and the Strymon, thus pushing forward the Persian dominion to the borders of Macedonia. Among the tribes which he conquered were the Perinthians, Greeks; the Pseti, Cicones, Bistones, Sapaei, Dersaei and Edoni, Thracians; and the Paeoplae and Siripasones, Pseonians. These last, to gratify a whim of Darius, were transported into Asia. The Thracians who submitted were especially those of the coast, no attempt, apparently, being made to penetrate the mountain fastnesses and bring under subjection the tribes of the interior.