The same appears to have been true for the cities of the Indus valley, of a like antiquity or nearly so. At Harappa the mud brick walls were ten to twenty feet high, and forty feet thick at the base. In some later civilizations "wall" and "city" were so tightly linked that one term could stand for the other. In classical Chinese a single character (cheng) was used for both city and wall. In early medieval Europe, Gregory of Tours (d. 594) could not understand why the substantial walled community of Dijon was not considered a civitas. As the town secretary of Eisenach put it many centuries later (1399), "What has a wall around it, that we call a city." By the same logic, a fifteenth-century map of the proud city of Pisa shows a complete circuit wall that never in fact existed. Whether in China under the Shang dynasty (1511-1100 B.C.) or at Great Zimbabwe in southern Africa or under Egypt's Fatimid caliphs, rulers imposed on their towns the social discipline needed to sustain gigantic building projects that could take decades, even centuries to complete. In some cases, as in parts of medieval Europe or the Hausa city-states of West Africa, townsfolk could impose the same kind of discipline on themselves.

A phenomenon that is global in scope cries out for comparative discussion. This volume is animated by the belief that comparison can enrich the separate histories that make up the history of the globe. Questions that have seemed fruitful in one part of the world may usefully be asked for others, and themes may take on a new importance when it is seen that they recur in many different regions. We leave to others the kind of comparison that seeks to use local or regional histories as foundation stones for a mega-history. It would be dubious in practice to make generalizations on the basis of a comparative scholarship that has been largely confined to European history, and it is arguably dubious in principle to assume that historical processes can be analyzed on quasi-Aristotelian premises, by envisioning a clear-cut distinction between local details or "accidents" and a common "substance" underlying all local manifestations of the process.

Of the nineteen essays presented here, eleven are devoted to Europe or to European settlements overseas, four to the Islamic world, two to China, one to sub-Saharan Africa, and one to North America. Our European focus reflects the fact that most of the work on walled cities is done by Europeanists, but it does not reflect the actual distribution of walled cities in the premodern world, when Europe's fortified towns were probably outnumbered by China's "thousands." We have been selective also in regard to topics, leaving out issues that in themselves are eminently worthy of comparative discussion. The essays presented here focus on three issues: What are the circumstances under which towns or their rulers choose to undertake the labor of surrounding cities with enceintes? How are particular programs of wall building - the construction of many urban enceintes in the same area over a relatively short period — linked to particular forms of warfare? And what are the symbolic meanings, cultural and political, that town walls acquire once they are built?

The five essays of Part I, "To Wall or Not to Wall," address the first question. No matter how "natural" it may have seemed for a town to have walls, the sheer labor and expense involved means that wall builders must have had compelling reasons. Most often, it was a matter of defense against anticipated attack.

GRAHAM CONNAH's survey of enclosed settlements in premodern tropical Africa finds that the main lines of development, including those leading to the massive mud walls of Benin and the stone towns of the Swahili coast, are indigenous. Full-blown seiges seem to have been rare, with walls and other enclosures intended more for protection against marauders (Chapter 1).

GEORGE MILNER's survey of palisaded settlements in eastern North America, from about 1000 A.D. to the seventeenth century, shows a clear distinction between the strongly built enclosures of the Mississippian culture zone, with its powerful chiefdoms, and the more lightly built palisades of northern settlements. The evidence points to scattered local warfare in both regions, albeit of a differing intensity (Chapter 2). These two essays show how a common human experience (warfare) leads to a common response (the enclosure of settlements). Some of these fortifications, like Benin's massive mud walls, were no less demanding in terms of labor and social organization than the stone or brick walls found in other parts of the world, and no easier to penetrate.

Turning to Europe, JAMES TRACY asks which towns got walled and which did not. For medieval Germany there is a scholarly literature rich enough to provide answers for such questions. The towns most likely to build walls were those that had a strong merchant community, or served a territorial ruler's need to secure his borders (Chapter 3).

KATHRYN REYERSON develops the perspective of burghers for whom the standing wall was more a present nuisance than a response to dimly remembered past dangers. Montpellier's officials turned a blind eye to the violation of laws aimed at preserving the wall's military function; stricter enforcement began only as war loomed on the horizon again (Chapter 4).

Finally, RICHARD KAGAN illumines the phenomenon of wall building by considering its absence in seventeenth-century Spanish America. Here the houses of religious orders and the settlements of converted Indians that clustered round the great cities were described as "spiritual walls," warding off the dangers of idolatry more effectively than any material walls might do (Chapter 5).

Part II, "Walls of War," examines the reciprocal relationship between changes in the character of warfare and what may be called programs of wall building, in which many cities in a given region were fortified over a relatively short period.

FREDERICK COOPER shows that massive city walls of ashlar masonry, described by Aristotle as "ornamental as well as useful for war," were an invention not of fifth-century Athens, but of Thebes under Epaminondas (d. 362 B.C.). These fortifications were intended not only to withstand new strategies for siege warfare, but also to secure the forward points of Theban hegemony (Chapter 6).

BERNARD BACHRACH points to the enduring legacy of late imperial Rome's program of urban wall building. In the barbarian successor states, as under Roman rule, the capture of fortified cities was the principal objective of warfare. Roman siege techniques were still in use in the Carolingian era, as was the Roman practice of militarizing urban populations by having burghers take responsibility for the defense of their walls (Chapter 7).

Turning to Islamdom, JONATHAN BLOOM argues for North Africa that "the notion of the unwalled early Islamic city is a myth." By examining three successive Fatimid capitals, of which Cairo (969) is the best known, he shows that Fatimid architects, sometimes thought to have imported the alien idea of urban wall building, actually drew on North African traditions (Chapter 8).

CATHERINE ASHER offers a diachronic survey of the walling of cities built on the site of modern Delhi, from the Indra-prashtra of Aryan legend to the Red Fort of Shah Jahan (1639). In most cases, the walls seem intended to hold off marauders rather than to sustain a siege; under the Mughals and their predecessors, Delhi was to be defended at the realm's frontiers (Chapter 9).

SIMON PEPPER seeks to dismantle the prejudice that any good work in Ottoman military architecture must have been the work of Christian craftsmen. Fortifications built along the main lines of Islamic-Christian conflict in the second half of the fifteenth century do not anticipate Italy's angled bastions, as has sometimes been argued, but they are designed in other ways both to absorb artillery fire and to provide gun platforms (Chapter 10).

Against the view which sees urban fortifications of the costly bastioned trace type as imposed in France by an absolutist monarchy on recalcitrant towns, MICHAEL WOLFE argues that French towns were eager to cooperate with the crown, even during the Religious Wars of the sixteenth century; fortifications in the new style were often built and paid for by the burghers themselves, using customary worksite traditions (Chapter 11).

Turning to the projection of European military power overseas in this era, MARTIN ELBL shows the Portuguese crown resisting as long as possible the expenses of new-style fortifications for its urban outposts in North Africa. Only after several towns had been lost to the Sa'dian dynasty were the three towns that remained under Portuguese rule refortified in the Italian style (Chapter 12).

Finally, GEOFFREY PARKER presents a broader view of the significance of the artillery fortress, as part of a military explanation for the rise of the West. In Asia, even old-style fortifications were sufficient to make European outposts virtually impregnable to assault. Only with the advent of Portugal's European rivals, notably the Dutch, did key sites begin to be fortified alia moderna. The successful indigenous powers were those that either copied European fortifications, or, like Japanese architects of the Tokugawa era, came up with artillery-resistant designs of their own (Chapter 13).

Part III, "Signifying Walls," examines what standing walls meant to contemporaries in terms of the city's place in the body politic, and in the larger cosmic order. A city wall is almost of necessity a symbol of sovereign power, because no government of more than nominal authority will permit the massive mobilization of labor and capital that wall building requires to proceed without its approval. At the same time, the well-ordered city is in many cultures the symbol of a larger cosmic order, and perfectly constructed walls can be the token of this earthly perfection that has meaning beyond itself.

NANCY STEIN-HARDT shows that the earliest extant images of Chinese cities, indicating perfectly rectangular outer walls and a separately walled government city within, bear a striking resemblance to modern illustrations, and even to conventional Western ideas about Chinese cities. Through the ages in China, every city must have walls, and walls that are known to have been irregular are represented as rectilinear, in keeping with an unchanging ideal (Chapter 14).

EDWARD FARMER examines hierarchical relationships among the perfectly modeled cities in printed gazetteers of the Ming period. Cities of higher administrative rank are invariably shown as larger than their subordinates, with larger gates and straighter walls, regardless of whether these conventions conformed to reality (Chapter 15).

SHEILA BLAIR shows how the massive Roman walls of the city known in the Islamic era as Diyarbekir were treated as a canvas on which successive rulers registered their claims to authority in ornate relief inscriptions. Of particular interest are inscriptions of the Saljuq era (1085-1093), in which Diyarbekir's ruler used the conventions of language and calig-raphy to counter the spiritual claims of the rival Fatimid dynasty in Cairo (Chapter 16).

WOLFGANG VAN EMDEN explores images of the city in French verse of the twelfth and thirteenth centuries. The distinction between a castle and a fortified city is not always clear, but both are represented as girt by impregnable walls reaching to the sky, often crystal white or brilliantly colored; the model for these dream cities is the New Jerusalem (Chapter 17).

SIMON PEPPER considers the implications of certain customs of siege warfare in Renaissance Europe: Unsuccessful defenders of fortified places were treated honorably in some cases, hanged in others. The telling point is that sieges were considered a test of sovereignty, so that he who exceeded the conventions of "reasonable defense" was deemed to have given offense to the victorious ruler, and was treated accordingly (Chapter 18).

Finally, MARTHA POLLAK examines graphic representations of the sieges of fortified cities in Europe from the early sixteenth to the late seventeenth centuries. Over this period, artists adopted mapmaking techniques for better depiction to scale, and learned to combine a bird's-eye or ichnographic plan with a curving perspective to display the wider horizon. Regardless of the techniques involved, the siege view was both a work of art and a trophy of war, showing forth the glory of the conquering prince, often portrayed at a central point of the design (Chapter 19).

Perhaps the most striking common theme to emerge from these essays is the association between royal power or sovereignty and the enclosure of towns. In North America it was the towns of the great Mississippian chiefdoms that had stouter palisades, reflecting a more organized and sustained pattern of warfare (Chapter 2). The siege and capture of walled cities was the strategic objective of warfare in the barbarian successor kingdoms of Europe, as it had been in the late Roman world, and monarchs of the sixteenth and seventeenth centuries used artistic representations of successful urban sieges as a way of publishing their glory to all (Chapters 7 and 19). Even in the Islamic world, often thought to be characterized by open cities, the capitals of great rulers like the Fatimid caliphs were walled as a matter of course (Chapter 8), as was each successive capital built by Delhi's sultans (Chapter 9); rulers also used town walls as a canvas for calligraphic proclamations of their titles and their accomplishments (Chapter 16).

In Renaissance Europe, a commander who defended his city more doggedly than the conventions of war prescribed was deemed to have offended the majesty of the town's would-be ruler (Chapter 18). By contrast, the notion that Europe's independent-minded burghers built and maintained their own walls, while not without foundation, has to be deemphasized in light of more recent studies of the relations between townsfolk, their rulers, and their walls (Chapters 3, 4, and 11).

Another important connection among many of the essays is the way programs of wall building are calibrated to perceived dangers represented by the military technology of possible foes. The ashlar masonry of Epaminondas' wall-building campaign represents a response to the torsion catapult (Chapter 6). Late Roman town walls had to be maintained or rebuilt in the early Middle Ages because the contending parties had mastered the techniques of Roman siege warfare (Chapter 7). Ottoman military architects found their own ways of responding to the new threat posed by siege artillery (Chapter 8). And in Europe's overseas expansion, the imperial powers looked at the kind of opposition they might face before deciding whether to build enceintes in the new Italian fashion, to remain content with older-style curtain walls, or not to wall their cities at all (Chapters 12, 13, and 5).

Readers will no doubt find other points of contact among the essays, or (perhaps more interesting) omissions that may call for further efforts in the same direction. This collection is meant not as the last word, but as the beginning of a comparative discussion.

Since many (though not all) of the walled cities discussed in this volume may be seen as related to a single grand tradition tracing back to the ancient Near East, it may be useful by way of an introduction to sketch the military-architectural inheritance that finds echoes in the later Christian and Islamic worlds.

Even before the rise of Sumer, the earliest town walls that have left an archeological trace were fitted out with special features that would be copied or reinvented again and again in later civilizations. Jericho's walls - surrounded by a dry moat and overtopped by a tower from which defenders could fire on their assailants — already serve to illustrate the important distinction John Keegan makes between a stronghold and a refuge. Refuges are sanctuaries against periodic raids, strongholds are meant to withstand a sustained siege by a foe capable of supplying his army in the field; hence in Keegan's definition a stronghold must enclose a supply of water, and must provide its garrison the means to wage an active defense.

At Babylon, early in the second millennium B.C., active defense was made easier by battlements atop the wall to shield defenders from the missiles of besiegers; by galleries projecting outward that permitted them to cover the base of the wall; and by towers all along the curtain at bowshot intervals that enabled them to rake attackers with flanking fire.

The town walls of the ancient Near East were not only surprisingly "modern" in a military sense, they were often more imposing than anything built subsequently. To my knowledge, no standing wall anywhere in the world can match the sheer opulence of the glazed brick surface of Babylon's Ishtar Gate, with its bright colors and bas reliefs. The city girded by multiple rings of walls, a fantasy suggested to "Utopian" writers of the Renaissance era by Plato's description of Atlantis, apparently existed in reality some centuries before Plato. A Hittite relief from ca. 1280 B.C. shows defenders fighting from battlements on three walls of a besieged city - two curtain walls and an interior citadel. Around 1100 B.C. the Assyrian conqueror Tilgath Pileser boasted of having laid waste "the three great walls" of the city of Hunusa "built with burnt brick." According to Herodotus, Ectabana, once the capital of the Medes, had had as many as seven concentric rings of walls, each overtopping the other; an Assyrian relief of the eighth century B.C., showing the Median city of Kishesim, conforms to this description.

Farther to the east, in a document of the second or third century B.C. describing Buddha's birth, the great city of Vaisali is said to have been girt by three walls, each one league distant from the other. But no structure of brick and mortar was proof against attack, especially as besiegers developed new ways of striking at the walls. Though the battering ram was known in Egypt as early as 1900 B.C., it was the Assyrians, ambitious conquerors, who put the ram on wheels and protected it from defenders' arrows by surmounting it with a turret to accommodate archers. The mobile siege tower was another Assyrian invention. The catapult, first developed by Sicilian Greeks (399 B.C.), was mainly an anti-personnel weapon for use by defenders as well as besiegers. The one-armed onager, better able to fling heavy stones against a wall, came somewhat later in the fourth century A.D.14 All the known elements of ancient siegecraft came together in the Greek world: Persian invaders brought sappers to undermine the walls, and the earliest recorded use of the battering ram in Greece was in 440 B.C.

Of necessity, Greek wall builders devised countermeasures. For example, the city of Rhodes (ca. 400 B.C.) pioneered a new principle of construction: Instead of having a brick (or stone) outer and inner wall encasing debris between them, the Rhodians built an outer curtain backed by a continuous arcade of deep arches along the inner side; this technique demanded less building material, provided better support for men and machines on the battlements, and also permitted breaches in the curtain to be repaired more quickly. Other Greek cities laid out curtain walls in zigzag segments to facilitate flanking fire from the towers and battlements. Still others (like their Mycenean forebears) built gate-approaches at an angle to the main wall, forcing would-be attackers to expose their right sides (not protected by shields) as they pressed forward. Some time during the fourth century B.C, the casemate or tower chamber fitted with slits for projectiles was developed as a means of protecting defenders' catapults from the effects of rain.

In the next century Archimedes (b. 287 B.C.) is thought to have invented the cutting of archer-loopholes into the wall during the siege of his native Syracuse. He also anticipated an element of the bastioned trace system by placing projectile weapons, defended by outworks, in front of the main walls to keep the foe at bay, incorporated other ideas from the East, like massive barbicans erected to shield approaches to the gates, or adaptations (machicolation) in the upper part of the curtain wall that permitted the building of projecting platforms from which defenders could fire directly down on an adversary who had reached the wall.

Ancient walls and their medieval refinements constituted as it were a dictionary of possibilities from which builders could draw according to their resources and requirements. The history of battlements -merlons behind which defenders shielded themselves alternating with crenels or open spaces - shows how ancient precedents could leave an imprint on the future even after the cities in question were long since buried by the debris of time. Merlons first appear on representations of Egyptian fortifications from the late third millennium B.C., and are rounded, as if to suggest the shields of soldiers standing atop the wall. Rounded merlons also turn up on bas reliefs showing fortified cities among the Hittites, the Assyrians, and, later, the Phoenicians and their Carthaginian cousins. Triangular or stepped merlons that would seem better suited to a brick wall appear first among the Assyrians, then on reliefs showing fortified cities in post-Mauryan India. The rectangular merlons better known from medieval European fortifications were apparently invented by the Greeks. The venerable antiquity of merlatura or crenellation helps to explain why, in sixteenth-century Europe, a ruler could have the battlements stripped from a city's wall as a way of proclaiming that it had forfeited the right of fortification.

Knowing that walls were once built in a certain way does not mean one will necessarily copy the past. For example, the Romans were aware of the Greek practice of building irregular, segmented walls, but chose not to follow it; instead, in walling their cities they often copied the pattern of the rectangular earthen rampart that always surrounded a Roman military camp. When town portals had to be protected in the troubled circumstances of the third century A.D., the Romans did so by building double gatehouses, a solution that was perhaps less daunting to a potential attacker than the angled gate-approaches known earlier among the Greeks, but more imposing to the onlooker. The sheer lack of funds was probably a more important reason for not imitating the best of what was known. Military engineers understood perfectly well the advantages of backing a brick wall on the inner side by an arcade of deep arches (as in ancient Rhodes) - in fact a city was hardly defensible without the solid battle platform that such arcades supported. Yet builders could not build more than what the town treasury could afford. For example, in the wall at Leiden, with its 50,000,000 bricks, arcades were added only as funds became available; by the time the Spanish army settled down before the city in 1573, the simple curtain wall was backed by arcades only at a few key points. The fact that Leiden's burghers successfully held off the foe for nearly a year - a victory of great moment in the Dutch Revolt - offers a useful caution against assuming that a town not fortified in up-to-date fashion could easily be taken.

Nonetheless, good fortification did make a difference, and perhaps most clearly so in the age of transition to the fortress architecture alia moderna, inaugurated by Italian military engineers of the late fifteenth century. The brilliant success of the "trace italienne" or bastioned trace was preceded and in a way necessitated by the brilliant success of the siege train, as developed by French artillery masters of the fifteenth century. In the last stages of the Hundred Years' War, Charles VII's siege train reduced as many as sixty English-held castles in a single season's campaign (1449); the city of Harfleur took four months to subdue in 1440, seventeen days in 1449.

By the 1460s, Italian military enterprisers like Federigo da Montefeltre, Duke of Urbino, were capturing fortified places by the use of mobile field artillery alia francese. Italian observers like Francesco Guicciardini, accustomed to a situation in which "the rulers of a state could hardly be disposessed," marveled at how fortresses were cracked open one after the other as France's Charles VIII (1484-1498) marched through Italy in 1494, en route to a short-lived conquest of the Kingdom of Naples. It was not just the throw-weight of projectiles that made the cannon of this era so much more effective than the onagers and trebuchets of an earlier time: since the gunpowder missile "travelled in a flat trajectory, it could be directed at the one point where a high wall is vulnerable to collapse, at its foundations."

The new system devised to withstand artillery bombardment had as one of its principal elements a low rampart. In a fully developed bastioned trace, a high curtain wall of medieval vintage was torn down and replaced by a low, stone-or brick-faced rampart that could absorb the shock of incoming cannonballs without giving way. In a less costly variant of the same principle, the old curtain wall remained standing while the suburbs beyond it were cleared to build a new-style rampart or "gun gallery" for the emplacement of cannon. In a pinch, a hastily built earthen rampart could serve to close a breach made by artillery in an old-style curtain wall. This expedient, known in Italy as a retirata, was used successfully by Pisa in its defense against the French (1500), by Fra Giocondo, Venice's military architect, in his defense of Padua against the armies of the League of Cambrai (1509), by the duke of Guise in his defense of Metz against Charles V (1552-3), and by the burghers of Leiden against the Spaniards (1573-4).

The second main element of the new system — the bastions properly so-called — was a series of triangular or spear-shaped gun platforms projecting at regular intervals, so constructed that the emplaced cannon could rake the ground at some distance in front of the rampart, while each point along the rampart was enfiladed by covering fire from opposite directions, with the inner loopholes or gunslits protected from besiegers' fire by the bastion's laterally projecting lobes. Fortresses equipped with bastions proved able to stand off or at least delay the advance of immense forces. In 1532 Nicola Juresic, castellan of Guns in Hungary, held out with his 800 men for twenty-one days against the armies of Suleyman the Lawgiver. In Italy, military planners were reluctant to undertake the siege of "artillery fortresses." By 1530, Michele di Sanmichele, by completely rebuilding the fortifications of his native Verona, had shown how the new principles could be applied to the defense of a large city.

In practice, however, few cities had the resources to support reconstruction on the massive scale that was required. Taking into account the outworks as well as the rampart and its ring of bastions, a fully built bastioned trace could take up as much ground as the area occupied by the city itself. The city as a form of human society was apparently not well adapted to enclosure within such a massive girdle: new fortress-cities would eventually be built in the alia moderna style, but none ever attained the population level envisioned by its builders. In fact, the practical need for multiple fortifications in the new style became apparent only as the available supply of heavy guns increased dramatically in Europe, during the second half of the sixteenth century.

Quentin Hughes believes that "nearly all the main towns in Europe were refortified in the second half of the sixteenth or at the beginning of the seventeenth century." But Simon Pepper and Nicholas Adams take a different view: As late as the end of the sixteenth century, "none of the greatest cities of Europe could boast a complete and fully bastioned enceinte." Yet if Europe's cities were slow in adopting the bastioned trace, more costly by far than a curtain wall, military strategists were even slower in devising means to attack the new fortifications successfully.

Not until Vauban, the military architect and grand strategist for Louis XIV (1660-1715), did planners perfect a system of entrenching that enabled attackers to enclose a city, guard against reinforcement, and advance step-by-step towards the bastions that were the key to its defenses. The military balance thus swung once again in favor of the offense, but at a daunting cost. In Vauban's opinion anyone expecting to take a properly fortified place needed a force at least ten times greater than that of the defenders. Hence the great sieges of the seventeenth century, like the fortifications against which they were directed, were turned into symbols of the awesome power of those few princes who controlled the resources of large and well-governed states.

One may say in conclusion that the recorded history of town wall building begins with the kings of ancient Sumer and ends with the rulers who disposed over the huge siege armies of seventeenth- and eighteenth-century Europe. The window on that great tradition that this volume affords begins with Epaminondas, the founder of Theban hegemony in Greece, and ends with Louis XIV of France.