The Royal Road

The fullest ancient description is a set-piece in Herodotus, written some two generations after Darius I and framed to explain to a Greek reader how far it was into the heart of the Persian world. He follows the road stage by stage from Sardis, the old Lydian capital and the seat of the western satrapy, eastward across Anatolia, over the Halys and the Euphrates, through Armenia and along the Tigris, down at last to Susa. All the way, he says, the traveller passes royal halting-places:

Everywhere there are royal stages and excellent resting-places.

Herodotus 5.52, trans. Macaulay^[1]

These stathmoi (stations) and katalyseis (inns) ran, he reports, through inhabited and secure country, with guard-posts and "gates" at the crossings of rivers and the passes into new lands. He then gives the reckoning that fixed the road in the Greek imagination: from Sardis to Susa there are 111 stations, and the distance is 450 parasangs, which he converts (at 30 stadia to the parasang) to 13,500 stadia, about 2,400–2,700 kilometres by modern reckoning, depending on the length assigned to the stadion. At 150 stadia a day, the walk takes ninety days; adding the stretch from the coast at Ephesus up to Sardis, the whole journey from the Aegean to Susa comes to "three months" on foot. The figures should be read as Herodotus's careful schema, not a surveyor's field-book (the round numbers and the tidy day-count are his ordering of the distance), but the shape is right, and the parasang (Old Persian frasang, the stage a caravan covers in an hour, roughly 5–6 km) is a genuinely Persian unit that outlived the empire.

Where Herodotus found the itinerary is a real question. The description follows his story of Aristagoras of Miletus, who came to Sparta carrying "to the interview a map of the world engraved on bronze" to persuade King Cleomenes that the march inland was feasible, and something like that map is presumed to underlie the account; Olmstead thought the tally read as though drawn "from still another official document".^[2][3] The stage-by-stage particulars, twenty stations through Lydia and Phrygia, twenty-eight through Cappadocia, the standing forts and guarded "gates" at the Halys crossing and the Cilician frontier, are not the kind of detail a Greek invented at a desk: some Persian road-book or official itinerary, however worn in transmission, evidently stands behind the passage.

Two cautions belong here at once. First, Herodotus describes one major documented route, the Sardis–Susa artery he had reason to know, not the whole imperial network, which was far larger. Second, the road was not a paved highway in the later Roman sense; the express service that ran on it "was more heavily reliant on swift mounts than on good roads", and the surface "seem[s] not to have been paved or well maintained".^[4] Olmstead went further, "roads we can scarcely call them": the Assyrians had laid paving and milestones near their cities, and there is no indication the Persians followed that example.^[3] The wonder of the Royal Road was never its engineering. It was its provisioning and its security: an unbroken chain of stocked stations and guarded gates through which a traveller with the King's warrant could move fed, mounted, and unmolested, in a world where every other road ran through banditry and dearth.

For all its fame, no one can draw the road on a map with confidence. "The route of Herodotus's Royal Road is still controversial, which is rather surprising", Briant writes, given how much has been written on it.^[2] The controversy sits in Anatolia. Most reconstructions carry the road north-east from Sardis on a great arc through Cappadocia, crossing the Halys twice on its way to the upper Euphrates; French argued instead, from Herodotus's own phrasing, that the road never crossed the Halys at all but struck south-east to meet the Euphrates at Tomisa, along the line of a later paved Roman road that would then be the Persian road's direct descendant. Against the southern route stands Herodotus's "Cilicia": the fifteen and a half parasangs he assigns it are far too few for the real Cilicia beyond the Taurus, and Jacobs reads the stretch as the district Strabo calls "Cappadocia at the Taurus", between the lower Halys and the mountains, which pulls the road north again.^[5] Where it crossed the Euphrates is equally unsettled (Zeugma has been proposed from satellite survey), and east of the Tigris the line is secure only in outline. Herodotus's numbers, in short, constrain every modern reconstruction and settle none: what one would expect of a genuine itinerary compressed for a Greek audience.

Upon the road ran the King's post, and it is this, more than the road itself, that became world-famous. The locus classicus is Herodotus's description of the mounted relay by which news of Salamis reached Susa. Fresh horses and riders were stationed a day's ride apart along the whole route, so that a dispatch was handed on like a torch in a relay-race, never pausing for the night or the weather:

These neither snow nor rain nor heat nor darkness of night prevents from accomplishing each one the task proposed to him, with the very utmost speed.

Herodotus 8.98, trans. Macaulay^[6]

And of the couriers themselves:

There is nothing mortal which accomplishes a journey with more speed than these messengers.

Herodotus 8.98, trans. Macaulay^[6]

Herodotus gives the Persian name for the riding-relay as the angareion, and the individual courier as an angaros; the word may derive ultimately from an Akkadian term for a written dispatch (egirtu), a reminder that the institution reached the Persians through the older bureaucratic empires of Mesopotamia.^[7] The term attested from inside the Persian record is pirradaziš, the Elamite spelling of an Old Persian *fratačiš, "express runner", and it appears in the administrative tablets from Persepolis as a real category of authorised traveller drawing rations on the road, almost invariably in connection with the King.^[5]

Xenophon, who had marched the empire's roads as a mercenary, credits the founding of the relay to Cyrus the Great and describes its mechanics exactly:

He (Cyrus) worked out what distance a horse could cover in a day when ridden hard but without collapsing. Then he set up horse relays at just those distances, and placed horses and grooms there.

Xenophon, Cyropaedia 8.6.17, trans. Kuhrt^[8]

Night-riders, he adds, took over from the day-riders, so that at full stretch "the service covers the distance faster than the cranes"; and whatever the truth of that, "it is plain that this is the fastest land travel on earth".^[8] The credit to Cyrus is the Cyropaedia's habit (it assigns Cyrus most Persian institutions) and cannot be checked; what the evidence shows is a road system already operating under Cyrus, and a maturing under his successors, for "it was probably during the reign of Darius that the system reached the perfection praised by Herodotus".^[5]

How fast was it? Herodotus does not actually give a relay day-count for Sardis to Susa; the figures in circulation are modern extrapolations, and a recent calculation (Colburn) puts the relay's Sardis–Susa run at about twelve days, against ninety on foot.^[5] Herodotus imagined each horse and rider posted a full day's journey apart; Hallock, editing the tablets, doubted the arithmetic, since a horse ridden hard all day yields no very impressive pace: "Actually there may have been a change of horses at each supply station, that is, every twenty miles or so", a geometry he compared to the American pony express.^[9] The courier's standing matched the institution's weight. Royal messengers were trusted intimates of the King, and the title could sit very high: Plutarch reports that Darius III had served as a royal courier (astandes) before he came to the throne, and in the older Near Eastern tradition the king's messengers were often royal kinsmen, empowered not merely to carry a message but to negotiate its terms.^[5] The institution left its mark on subject literatures too: in the book of Esther the King's edicts go out sealed with his ring and carried by mounted couriers to every province (Esther 3.13, 8.10–14).^[5]

What is certain is that the speed astonished contemporaries. A later Greek philosophical text, imagining how a single unseen king might govern a whole world, reached for the Persian communications system as its very image:

All the Empire of Asia, bounded on the west by the Hellespont and on the east by the Indus, was apportioned according to races among generals and satraps and subject-princes of the Great King; and there were couriers and watchmen and messengers and superintendents of signal-fires.

Pseudo-Aristotle, De Mundo 6 (398a), trans. Forster^[10]

The same text adds the beacon-chain, fire answering fire along the heights so that word of a distant frontier reached the King between one day and the next:

So effective was the organization, in particular the system of signal-fires, which formed a chain of beacons from the furthest bounds of the empire to Susa and Ecbatana, that the king received the same day the news of all that was happening in Asia.

Pseudo-Aristotle, De Mundo 6 (398a), trans. Forster^[10]

The "same day" is surely rhetorical, and the beacons carried only pre-arranged signals, not messages, but that the empire's speed of knowing had become, for Greeks, the standing figure of imperial power is itself the point. Nor were beacons the only auxiliary channel: Diodorus describes a chain of lookouts posted across the valleys of Persis, men chosen for their voices, who could shout a summons from post to post so that it crossed a thirty-day journey in a single day, and Antigonus, organising his eastern territories in 315 BCE with beacons and dispatch-riders, was plainly running surviving pieces of the Achaemenid machine.^[2]

The Sardis–Susa road was the best-remembered strand of a system that ran, in fact, across the whole empire. Herodotus described the artery he knew; the network reached every quarter of the King's lands, and in the Persepolis travel-texts "the entire empire was linked together by a network of roads": the destinations run from Sardis to Bactra, India, Arachosia, Carmania and Egypt, and, in Briant's summary, "the entire imperial territory is covered", the road from Sardis to Susa "just one royal road among many others".^[2] Ctesias, the Greek physician who served at the court of Artaxerxes II, closed his Persica with a survey of the whole system seen from its western end: "In it he described the relays (stathmoi), days elapsed, and parasangs between Ephesus and Bactra and India", reports Photius, the Byzantine patriarch whose summary is all that survives of it.^[11] Even the bare notice matters: a road-book running to Bactria and India in the 390s BCE means the eastern network was intact and administered late in the empire's life, well after the loss of Egypt.

From the capitals the roads fanned out and interlinked: Susa, the lowland administrative seat where the great road ended (though the road itself ran on, to Persepolis, Carmania and India); Ecbatana, the Median highland city; Babylon, the vast Mesopotamian hub; and the dynastic ceremonial seat at Persepolis, itself a working node in the ration-system. Eastward an artery ran through Media toward Bactria and the borders of India, with a further route reaching the Indus through Makrān; in the west a road ran from the head of the Mediterranean at the Gulf of Issus through Anatolia up to Sinope on the Black Sea, linking the Aegean world to the Transcaucasus and the north; and southward the roads bound in Egypt. The tablets' toponyms are more than destinations: they map an administrative geography of regional centres, from Anshan in Persis to Taoce on the Persian Gulf, each authorised to issue travel documents, with the mobile royal court itself counting as one such centre, so that a pass could be issued "from the King" wherever he happened to be.^[5] A satrap's chancery at the far edge of this web could correspond with the centre and with its own subordinates over these roads; the fourth-century Aramaic letters of the Bactrian satrap Akhvamazda to his officer Bagavant show such correspondence in action, carried by named couriers bearing sealed authorisations.^[12]

Movement over the network can even be timed. The Hellenistic historians, whose armies marched the same roads within living memory of the empire, supply durations: Babylon to Susa in 22 days; Susa to Ecbatana in 40 by the royal road through Babylonia, or in nine by the direct and dangerous path over the Zagros; Ecbatana to Persepolis in about 20.^[2] The Susa–Ecbatana doublet is instructive: the royal road was four times slower than the mountain short-cut and was the road of choice anyway, because a caravan needs water, fodder and security more than geometry.

The land network worked alongside a system of waterways. In Egypt the Nile was the principal artery; in Mesopotamia the Euphrates, the Tigris and the canals carried official and private traffic (boats and crews were hired from private owners for government service), and the journey from Babylon to Susa was by preference made by water.^[5] Darius pushed the water-net outward: Scylax's voyage down the Indus and round Arabia, made on the King's orders, charted a sea-route from India to Egypt, and the royal canal from the Nile to the Red Sea, commemorated in Darius's own inscriptions, joined the Mediterranean world to the Persian Gulf.^[5] The stations of the land-roads, for their part, were not built for casual travellers: they served officials, couriers, and authorised parties on the King's business, and to use them one had to hold the King's warrant.

The genius of the system lay in its stations. Spaced roughly a day's ride apart, each was a stocked node where a courier could change mounts and an authorised traveller could rest, water, and be fed. As Kuhrt puts it, the tablets' evidence that the stations stood a day's travel apart "is a reminder of how dense was the web embracing the imperial territories".^[2] The stations held the horses and men that made the relay possible; the guarded "gates" at rivers and frontier-passes policed who moved and how. This was expensive, standing infrastructure, and the empire paid for it not chiefly in coin but in kind and in obligation: the surrounding country supplied the horses, the fodder, and the provisions, and later dynasties that inherited the institution would exempt a locality's taxes in exchange for maintaining its post-station. The whole apparatus depended on the King's authority being felt at every link in the chain: a station that was not provisioned, or a stretch of road that was not secure, broke the relay as surely as a felled bridge. That the Achaemenid roads were so consistently kept, across so many satrapies and so many languages, is itself a measure of how real the King's reach was; when central authority later failed, the same post-stations went hungry and the couriers turned to plunder, as the record of the system's medieval afterlife repeatedly shows.^[4]

For a long time the Royal Road was known only from the outside, through Greek eyes. The Persepolis Fortification tablets (tens of thousands of Elamite administrative clay documents from the reign of Darius, recording the movement of commodities through the heartland around 509–493 BCE) transformed that: the road-system becomes visible as a working bureaucracy rather than a Greek wonder. A large share of the texts record travel rations: flour, wine, beer, and fodder issued to parties moving between named places, from Susa and Persepolis to nodes across Persis and Elam. Crucially, the travellers carried a sealed authorisation (a halmi, a "road-pass" issued by the King or by an official of satrapal rank) that stated the scale on which the bearer was entitled to be fed at each station. The pass, halmi in the tablets' Elamite, rendering an Old Persian *viyatika, functioned, in Briant's words, "as both a safe-conduct and a permit to travel", naming the size of the party and its entitlements.^[2] Some texts name the origin of a journey and the issuer of its halmi; a number record the King himself issuing the pass.

The vouchers survive in quantity, and a single specimen shows the machine whole:

4.65 bar of flour, Dauma received. Each of the 23 men received 1.5 qa, and 1 qa for each "boy" (puhu). Dauma bore a document sealed by Irdarpirna. They were traveling from Sardis. They were headed to Persepolis. Month 9 of year 27. At Hidalu.

Persepolis Fortification tablet PF 1404, trans. Briant^[13]

Behind those six lines sits the whole system. Irdarpirna is Artaphernes, Darius's brother and satrap of Sardis; in 495 BCE his sealed authorisation, issued in western Anatolia, was honoured at Hidalu on the border of Elam and Persis, and the flour disbursed there was debited to his account when the receipts were collected and reconciled at Persepolis.^[13][9] A seal cut at one end of the empire commanded provisions at the other; the satrapal and royal seals were, it appears, recognised throughout the King's lands.^[5] And the ledgers record every rank of traveller: "1 woman went from Susa (to) Kandahar. She carried a sealed document of the king, and she received (it)." She went in the care of an "elite guide", one of the official escorts the administration assigned to parties needing guidance or protection, Indians, Cappadocians, Sardians, Skudrians and Egyptians far from home among them.^[13][9] The express couriers, the pirradaziš, appear drawing their rations singly or with a companion or two, riding "express" post horses permanently maintained at fixed stations, their fodder accounted by the month.^[9]

The roads also had their own police. The tablets ration armed teams of spear-bearers described, literally, as "road counters", once taken for surveyors; the equivalent titles show that "their assignment clearly had to do with controlling rather than with measuring", and one text has such a team inspect a stretch of road and then wait at a station for the King himself to come up it.^[5] Seals were the system's signature, "even the most modest traveler was expected to have a personal seal", and the rare traveller who stamped a receipt with an earring or a coin proves the rule.^[5] The machine could fail in recognisably modern ways too: one memorandum concerns "a previous travel authorisation lost on the road".^[5]

This is the Royal Road turned inside out: not a monument but an accounting system, a web of entitlements and seals and issued grain by which the crown fed and controlled everyone who moved on its business. It confirms Herodotus's stations and inns from within the Persian record, and it corrects the romance, showing the road as an instrument of administration, a thing of ledgers and clay, before it was ever a marvel.

The tablets mention the sealed pass constantly and never preserve one; the vouchers were filed at Persepolis, the warrants travelled on with their bearers. By an accident of survival, the single specimen that does survive comes from the empire's other end: a letter in Aramaic on leather, now in the Bodleian Library at Oxford, written in the late fifth century BCE for Aršāma, satrap of Egypt, who was away from his province (in Babylonia or Elam) and needed to send his Egyptian steward Nakhthor home. The letter is addressed by name to seven officers along the route, at Lahiru, Arzuhina, Arbela, Salam and Damascus among other stations, each responsible for issue within his own district, and instructs them to ration Nakhthor's party daily on a stated scale: two grades of flour, wine or beer and a sheep for the steward; a measure of flour each for his ten servants and for the two Cilicians and the craftsman travelling with him; fodder for the horses. It ends with the formulae of a working chancery:

give them these provisions, each officer of you in turn, in accordance with (the stages of) his journey from province to province (medinah) until he reaches Egypt; and, if he is more than one day in (any) one place, do not thereafter assign them more provisions for those days. Bagasaru is cognizant of this order: Rasta is the clerk.

The Aršāma warrant (TAD A6.9), trans. Briant^[14]

Every clause earns its keep. The officer-by-officer address maps a real itinerary across Upper Mesopotamia and Syria, the Arbela–Damascus branch of the great east–west artery; the ration-scale grades the party by rank exactly as the Persepolis ledgers do; and the one-day rule (linger, and you feed yourself) polices the crown's costs while confirming the day's stage between stations. Because the rations are charged to Aršāma's own estates, the letter has been read as evidence that the satrap held lands the whole length of the route; the more economical reading is that the named officers were the regional officials who oversaw issue at the way-stations, with the cost booked against Aršāma's account precisely as a tablet debits Artaphernes.^[14] A journey crossing several satrapies may in any case have needed layered paperwork: the warrant reads naturally as a master-authorisation from which stage-passes could be issued, and one Persepolis text shows a party of 94 travellers from Lydia arriving on a replacement authorisation issued en route by the satrap of Susa.^[5]

What the couriers were to information, the roads were to force. The military purpose of the network is explicit throughout the sources: levies answering a call-up moved along it, and "when armies were on the move, commanders needed to be able to rely on sufficient stores for men and animals", stores it fell to the local governors to gather.^[2] Xenophon's Greeks, retreating up the Tigris, rested three days in villages stocked with flour, wine and barley "collected by the satrap in charge of the district"; ostraca from the Negev show garrisoned stretches of road with locally supplied depots.^[2]

The royal roads were built for wheels. The ancient descriptions call them "wheelworthy" (hamaxitos), broad enough for baggage-trains, war-chariots and the four-wheeled travelling wagons of the great; even so, heavy rain could still stop an army.^[2] Keeping them open was heavy, continuing labour. The tablets appear to know a specialised roads corps; the army carried its own pioneers (Xenophon's Cyrus details spearmen with axes, archers with mattocks and slingers with shovels to march ahead of the wagons); Xerxes set a third of his army to cut a road through the Macedonian forests in 480; and behind them all stood the requisitioned labour of the kurtaš and the peasant corvée that everywhere in the ancient Near East kept the king's road open.^[2] The satrap maintained the stretches crossing his territory, down to selling off the trees that fell across them; the road Xerxes marched into Greece was still visible, unploughed and held in reverence by the Thracians, when Herodotus wrote two generations later.^[2]

The strategic geometry cut both ways. When Cyrus the Younger marched against his brother in 401 BCE, he avoided the stocked and guarded royal road through northern Mesopotamia precisely because to use it was to be seen, and led his army down the barren left bank of the Euphrates instead, where the pack animals starved, prices in the camp market ran to an estimated fifty times those of contemporary Athens, and the wagons stuck in mud a maintained road would have spared them.^[2] To move openly on the King's roads was to move under the King's administration; to evade them was to fight the country itself.

What the roads carried, above all, was the King's will. Communication in the empire was overwhelmingly a matter of the written order sent down through the administration, and the medium was very often Aramaic, the chancery lingua franca that let a message dictated in one tongue be written, carried across the empire, and read out or rendered in another. "Letters and decrees conveyed by emissaries and messengers using the empire-wide road system and its way-stations" were the sinews of government.^[12] A subject who wished to travel safely wanted, above everything, the King's own paper, as the Judaean official Nehemiah knew when he stood before the King:

If it please the king, let letters be given me to the governors beyond the river, that they may convey me over till I come into Judah.

Nehemiah 2:7, KJV^[15]

The other face of protection was surveillance. The roads were watched, and the watching was proverbial. When the exiled Spartan king Demaratus wanted to warn Sparta that Xerxes was coming, he scraped the wax from a folding tablet and wrote on the wood beneath, re-waxing it "so that as the tablet was carried it would reveal nothing to the guards along the road".^[2] The anecdote is probably invention; its premise, that nothing crossed the empire unexamined, is what every source takes for granted. Themistocles, travelling in Persian service, was nearly murdered at Leontocephalae, a stop on the royal road, by hired Pisidians who were in all likelihood men of the regular road patrols, and saved himself by a side road; Alcibiades, refused a satrap's permission to go up to the King, set out secretly along the road from Dascylium and was hunted down and killed in a Phrygian village.^[2] Access to the roads was jealously guarded, and the network that carried the King's word down carried the reports of his inspectors, the officers the Greeks called the King's Eye, back up: to travel was to be seen, logged and fed by the same administration.

Royal paper opened the roads that royal soldiers guarded. But the same reach that provisioned and protected a loyal servant was, for a servant grown too great, a leash, and, at need, a noose. The empire's richest political drama, the "bind of the great servant", turned on exactly this: the King could reward a satrap with land and access and the shares of his own table, yet the arteries that carried those gifts carried also his recall. The classic case is Oroetes, the over-mighty satrap of Sardis, who had defied Darius and killed a royal messenger. Darius undid him by the road itself: the same relay that had carried the satrap's honours carried, sealed, the order for his death, read out by a courier to the man's own guards.^[16] The bearer of such a letter did not always fare better than its target; a courier might carry, folded into the day's business, the order for his own death, as the Spartan Pausanias's messenger found:

He undid the letter, and found the postscript that he had suspected, viz. an order to put him to death.

Thucydides 1.132, trans. Crawley^[17]

The road was the King's longest arm. It reached to reward the faithful and to end the dangerous, and along it flowed everything that made one man's word law from the Aegean to the Indus, the standing image, to the Greeks, of what it meant to be ruled by a King of Kings.

It is tempting to imagine the road-and-post system as a great engine of royal propaganda, broadcasting the King's image and message to his subjects. The evidence urges caution. The most careful recent treatment (Bruno Jacobs, in the Encyclopaedia Iranica) argues that Achaemenid royal communication was, in the main, top-down administration (orders and messages to officials) rather than ideological penetration of the population; the great monumental inscriptions were addressed chiefly to the gods and to future kings, not to a general public who could not in any case read their archaising Old Persian. Even the Behistun inscription, the one text Darius says he had copied out on clay and parchment and "distributed" through the lands, is the exception that proves the rule. The roads carried the machinery of a state, not the messaging of a modern regime, and "a real ideological penetration of the empire by the Achaemenid rulers did not take place".^[12] The 2021 synthesis reaches the same verdict from the administrative side: "An explicit imperial ideology underpinning this cohesion is not in evidence"; the empire's integration was "rooted primarily in more pragmatic levels of administration", in the daily traffic of orders and accounts between offices.^[5] The Royal Road's true work was quieter and more fundamental: it made governance at a distance possible at all.

For a system so famous, the road itself long went unseen; that has begun to change. North-west of Naqsh-e Rostam a stretch of the Persepolis–Susa road has been traced for 43 kilometres, running along the edge of the Marv Dasht plain at a slight elevation to keep it above the Kur river's floods, its rock-cut passages five metres wide.^[18] At Bard Burideh an excavated section, also five metres wide, "was construed from 15 cm deep stone gravel sealed with reddish soil, and was lined with curbstones", and ran onto an 82-metre stone causeway carrying a wooden bridge: graded engineering, if not pavement.^[18] The stations are emerging too. Two way-stations have been identified at 26-kilometre spacing between Naqsh-e Rostam and Ram Gerd; another was excavated in the Tang-e Bolaghi gorge near Pasargadae; and at Deh Bozan, on the great Khorasan road north-west of Behistun, the remains of a six-columned, wooden-roofed lodge with polished stone column-bases give a first picture of what Herodotus's "excellent resting-places" looked like on the ground.^[18] Surveys from Khuzestan to the Surkhandarya valley of Bactria have tentatively identified further stops from the spacing of sites alone.

The measured intervals, 16 to 26 kilometres, bracket the roughly 24-kilometre average implied by Herodotus's 111 stations, and the excavated surfaces confirm the philology, for on paving "the archeological record is mostly negative".^[18] What made a royal road royal was not stone but upkeep: grading, width, causeways, bridges and the manned, provisioned stations, renewed year after year across the breadth of the empire. Alongside the working stations stood a rarer class of buildings, the "pavilions", some of them far from the main routes: not relay-posts but local seats of royal authority, lodging the court, royal women and high officials on their progresses.^[18] Permanent bridges are attested at Babylon and at Pasargadae; the great rivers were otherwise crossed by ferries, fords and bridges of boats, which Herodotus's itinerary and Xenophon's march count off river by river.^[2]

The Achaemenid road-system outlived the dynasty that built it, and this is perhaps the surest proof of how good it was. When Alexander overthrew the empire, he conquered it along its own roads, using the arteries and stations Darius's house had laid down to move his army into the Persian heartland. The relay-post itself was inherited and re-inherited for a thousand years and more. The Sasanians ran a comparable system, and by a peace-treaty with Byzantium in 561 CE both empires undertook to supply envoys with mounts at their postal stations. The Muslim conquerors took it over as the barīd (a name descended, through Greek, from the Latin veredus, the courier's horse). The Mongols built their relay-stations, the yām, along the arteries of their vast realm, with fresh horses kept ready for the Khan's couriers. Under the Safavids and Qajars the rider was the čāpār and the relay-post the čāpār-ḵāna, until in the nineteenth century the telegraph and then the motor-car at last made the galloping courier obsolete.^[4] The line runs unbroken from Darius's pirradaziš to the post-house of the modern age, and the most famous words ever written about that whole tradition, the promise that neither snow nor rain nor heat nor gloom of night should stay the courier, began as Herodotus's account of the Persian post, and, in the familiar paraphrase carved over the main post office of New York City, describe it still.^[9]