In 1395 the crusading propagandist Philippe de Mézières sent an eloquent plea for an Anglo-French crusade to Richard II of England. 'Remember', he wrote:

... that the Holy Catholic Faith, for which so many of your ancestors, the blessed kings of England suffered martyrdom, today in Jerusalem and Syria, Egypt and Turkey, and throughout the East, is trodden under foot, dishonoured, deserted and abandoned... and the divine sacrifice and Office forgotten and held in abomination... God grant that you two kings (Richard and Charles VI of France) may do all that remains to be done, to the consolation of all good people.

De Mézières wanted the two kings to bury their differences and set out on crusade for the East together. He said that he had the perfect military instrument to offer them:

This simple medicine... is none other than the blessed new Order of the Passion of Jesus Christ, conceived forty years ago under God's inspiration, and now to be submitted to the devotion of your Majesties.

De Mézières, an ex-chancellor of King Peter of Cyprus now living in retirement in Paris, had made the launching of a new crusade the driving ambition of his life. From the mid-1360s he had penned one passionate plea after another for action against the lnfidel; and around 1368 he had launched his own crusading Order. By the early 1590s the political circumstances of Europe seemed to favour the realisation of his ambition. Hostilities between England and France had been ended by a truce, and Richard and Charles seemed disposed to join forces. Charles' kinsmen, the dukes of Orleans and Burgundy, were, by May 1395, seeking financial support and negotiating for allies. Difficulties had been caused a year earlier by the outbreak of a rebellion against John of Gaunt's rule in Aquitaine which largely put paid to English participation. Nonetheless, in April 1396, a force of 10,000 or more under Philip of Burgundy's son John set out. Its main aim was to strike deep into Turkish territory in the Balkans.

Successful assaults were made on the Turkish fortresses of Vidin and Rahova, and in September the key Danubian fortress of Nicopolis was invested. But by now a relieving force under the Sultan Bayezid was on its way. South of Nicopolis, on September 25th, the decisive engagement between the two sides was fought. Details of the fighting are obscure, but it seems that the French and Burgundian knights recklessly charged forward, much as their forbears had at Crecy. The predictable massacre followed, and the Western army was destroyed.

The disaster at Nicopolis brought to an end nearly a generation of intense crusading activity. The immediate spur to it had been the rapid Infidel advance into Europe. By 1348, the Ottoman Turks had established a bridgehead into Europe at Gallipoli, and by the 1350s they were pouring into the Balkans. Edirne fell to them in 1361, Plovdiv in 1365, and in 1571 a victory at Maritsa gave them control of most of Macedonia. By 1389, when they extinguished the Serbian kingdom at Kossovo, the whole of Central and Eastern Europe lay open to their advance. The response on the Christian side was a series of initiatives by the papacy and 'front-line' leaders. Pope Clement Vl organised an anti-Turkish coalition in the East in 1344, which succeeded in taking the port of Smyrna. The swashbuckling Peter of Cyprus captured Antalya in 1361, and four years later briefly took possession of Alexandria. Later, in the 1360s, Count Amadeus of Savoy led an expedition which succeeded in recovering some Black Sea cities fox the Byzantines.

Underlying this often frenetic activity against the Turks lay a much deeper enthusiasm for the crusade. In the minds of many late-medieval faithful there remained a powerful commitment to the Holy Land. This manifested itself in a variety of ways. As Dr Tyerman has shown, prayers were often said by guildsmen in England for the Holy Land. In a fraternity at Wiggenhall, Norfolk, meetings began with prayers 'for the Holy Land and the Holy Cross... that God might bring it out of heathen power and into the rule of Holy Church'. In many upper-class households relics of crusading were still cherished: in 1376, for example, Mary, Countess of Pembroke possessed a 'cross with a foot of gold' which her long-deceased father-in-law had brought back from the Holy Land. At the same time, pilgrimages to Jerusalem were still very popular. Among Englishmen who visited the Holy City were Henry Boling- broke (the future Henry IV), Thomas, Lord Clifford and the Earl of Warwick. Among less exalted pilgrims was the Gloucestershire knight Sir John de la Rivière who in 1346 combined a pilgrimage with spying on the Turks.

If crusading drew on a deep well of popular enthusiasm, it nevertheless appealed in particular to the military élite. As Maurice Keen has shown, participation in crusading brought a nobleman renown; in Keen's words, 'it carried a special, sovereign honour'. There was often a link between crusading and the secular Orders of chivalry which flourished in the later Middle Ages. For example, Peter of Cyprus' Order of the Sword had its origins in the king's crusading plans, and it lived on after his death as an association of nobles visiting Cyprus who committed themselves to fighting the Turk. Equally, the regulations for Louis of Taranto's Company of the Knot (1352) and Charles of Durazzo's Order of the Ship (1381) both contained rules obliging members to take part in a crusade to recover Jerusalem, to which Louis and Charles both had claims.

However, it was less in the military Orders than in the careers of individual knights that the aspirations of the age found most obvious fulfilment. Dozens, even hundreds, of knights from England, France and elsewhere can be shown to have gone East. A neat illustration is provided by the inscription on the brass of Sir Hugh Johnys (c. 1500) at Swansea, which records that Hugh not only fought for five years in the wars against the Turks but had actually been knighted at the Holy Sepulchre at Jerusalem. Hugh's experience was not particularly unusual. Sir Richard Waldegrave, who was to be Speaker of the Commons in 1381, had fought against the Infidel in Prussia, had assisted in the taking of Antalya and had been present at the storming of Alexandria. A contemporary, Nicholas Sabraham, on his own admission 'had been armed in Prussia, Hungary, at Constantinople, at the Bras de St Jorge, and at Messembrid'. Quite possibly, someone like Waldegrave or Sabraham provided the model for the crusading Knight of Chaucer's Canterbury Tales. A century later a Buckinghamshire knight, Sir John Cheyne, was noted on his brass as having combatted the Turks, slain a giant and visited the Holy Sepulchre.

Although the widespread crusading activity of the late Middle Ages is well documented, historians have often underestimated its appeal because there were no general passagia (crusades) in the period, Grand set-piece passagia to the East largely died out in the 13th century. The crusades of the late Middle Ages were smaller and more limited in objective; however, they were staged more frequently, and in more varied locations. In the 1340s, for example, there was a flurry of crusading activity in Spain following a major Muslim advance from North Africa; in 1342 knights from Germany, England and France were present when Alfonso of Castile took Algeciras. Again in the 14th century there was regular campaigning in the Baltic against the heathen Lithuanians. John 'the Blind', King of Bohemia, Henry Duke of Lancaster, and the future Henry IV again, were among the Western notables who joined the Teutonic Knights in their raids into the (until 1385) heathen wastelands further east.

However, late medieval crusades were not only preached against the Infidel. To the disapproval of critics like Bartholomew of Neocastro, they were also preached against fellow Christians. Crusading against Christians was not new; indeed, it was inherent in the very definition of crusading. A crusade, according to the most widely accepted definition, was a holy war preached against Christendom's enemies by the pope, in which the participants gained the benefits of an indulgence. As repeated challenges to the Church's authority had made clear, Christendom's enemies could be internal, as well as external. In the 13th century crusades were preached against popular heterodox groups, such as the Cathars in southern France, and political enemies of the papacy, like the Emperor Frederick II, while in the mid-14th century the weapon had been used against the routier companies threatening Avignon.

In the years of the Great Schism from, 1578 to 1417, however, crusading against fellow Christians became more controversial. This was partly because some blatantly political crusades were preached – the most notorious being the bishop of Norwich's crusade against the pro-French cities in Flanders. But it was also because heterodox groups were becoming more common. In England, for example, the Lollards, the followers of John Wyclif, became an active force from the 1380s and, in the following century, the Hussites took over the state in Bohemia. Both Lollards and Hussites were highly critical of crusading. Hus denounced it as testimony to the Church's internal corruption.

It has sometimes been argued that political manipulation of crusading by the papacy contributed to its decline in the 15th century and later, but it is doubtful if this was the case. A number of 14th century knights can be shown to have enlisted in crusades against Christians as well as more orthodox crusades. John Holland, Earl of Huntingdon, Richard II's half-brother, for example, fought in John of Gaunt's 'crusade' in Spain from 1386 and negotiated with Boniface IX for an anti-Avignon crusade in 1397. The signs are that service in a crusade against fellow Christians was assimilated into the general chivalric culture of the age.

So why, in that case, did crusading eventually wither and decay? Part of the reason is that, with the passage of time, the goal of recovering Jerusalem receded further and further towards the horizon. After the extinction of the Crusader Kingdom in 1291, in the wake of the fall of Acre, taking Jerusalem was no longer a practical military proposition. As a result, something of the drive, something of the enthusiasm and passion, which had driven 12th century crusading ebbed away. It is true that there were plenty of other crusading destinations. An obvious one was Egypt: as St Louis had recognised, if Egypt fell, Palestine would probably fall later; and in the 14th century, as we have seen, there were many other eastern Mediterranean destinations. But the very vitality, the rich pluralism, of crusading was a source of weakness. For the more diverse it became, the more incoherent it became too – and ultimately the less successful. The key element of direction was lacking.

However, there was another, and perhaps a more important, reason for the decline of crusading. Gradually, as Norman Housley has argued, crusading was rendered impractical by adverse developments in Europe's political, military and financial structures. Although crusading as an ideal survived, at least up to a point, the institution itself perished. A number of factors can be identified as contributing to this, Growing distrust of papal leadership was one. In the 14th century, when it was based at Avignon, the papacy was widely perceived, particularly in England, as being sympathetic to the French. Secondly, the levying of public taxation to pay for a crusade became more difficult once such taxation came to be sanctioned, as it generally was in England and France by the 14th century, only for national defence.

Finally, the long and bitter wars of the later Middle Ages, most notably the Hundred Years' War between England and France, made collaboration between rulers ever more difficult. It is no coincidence that the last general passagia took place in a period of relative peace – the 13th century.

Yet the remarkable feature of crusading in the late Middle Ages is not so much that eventually it declined, as that it flourished for so long. Even in the 15th century, when the tradition of passagia to the East had virtually ceased, crusading remained part of the body of ideals which the chivalric élites, and even hard-headed kings and princes, took for granted. The court which appears to have been most strongly influenced by crusading ideas was the Burgundian. The Valois dukes had, of course, long been associated with crusading. Philip the Bold, the first duke of his line, had taken the Cross in 1365 and had regularly subsidised crusading in Prussia. John of Nevers, Philip's son, had been the commander of the force that had been defeated at Nicopolis. But John's son, Philip the Good, was the dynasty's greatest enthusiast. At a celebrated feast – the Feast of the Pheasant – at Lille in February 1454 Duke Philip had a live pheasant brought into the hall and swore on it that he would undertake a crusade provided that at least one other ruler also took the field. At a later stage the duke went further, swearing to take on the Grand Sultan in single combat. Perhaps surprisingly, a practical proposal emerged from this prodigious showmanship: in 1456 a report was drawn up showing how an actual crusade could be organised. Old age, however, prevented the duke from putting any of its recommendations into practice.

A ruler like Philip the Good realised that involvement in crusading could bring a dynasty fame and prestige. More than that: he probably realised that it could bring these benefits regardless of outcome. It is a curious paradox that in 1596, when John of Nevers returned from Nicopolis, he was fêted as a hero even though he had been defeated and had suffered imprisonment. Failure did not matter. John had won renown fox himself, and his experiences in the East were instrumental in winning legitimacy for his dynasty.

Yet, for all the importance of la gloire, there was a less wordly aspect to the appeal of crusading. Late medieval princes were deeply conscious of their status as personae mixtae: in other words, the fact that they were both priest and layman. To realise the spiritual aspect of their persona they increasingly manifested an interest in matters of piety and public religion. For example, they encouraged the moral reformation of their households; they made lavish religious benefactions and mass endowments. And, more relevant here, they maintained a personal commitment to the crusade. A clear illustration of (his is provided by the policy of England's Henry VII. Henry demonstrated his crusading interest from almost the beginning of his reign. In late 1485 he ordered prayers to be said throughout England for the success of Ferdinand and Isabella's offensive against the Moors of Granada. Later he promised the Spaniards an English contingent, and by May 1486 a force under the command of Sir Edward Woodville, the queen’s uncle, was distinguishing itself in the capture of Loja in Granada.

In the final years of his reign Henry developed an interest in the crusade to the East.. In 1502 he sent the Emperor Maxmilian £10,000 to help fight the Turks, and two years later he handed to the pope at least £4,000 from the 1502 crusade tax. In the light of all this, it is hardly surprising to find that Henry was regarded as something of a crusade enthusiast: in 1506 he was made 'protector of the Order of St John of Jerusalem at Rhodes', a hitherto unique privilege; while in 1508 Wolsey reported that the imperial negotiators had called Henry 'the most suitable instrument of Christ to defeat the enemies of the Christian religion'.

The point that emerges from all this is that crusading became associated in kingly minds with Christian renewal. The connection had been manifested in English kingship as early as Henry V's reign. Henry, a royal dévot, had sponsored a policy of religious renewal at home, repressing heresy and encouraging deeper spirituality; and at the same time, according to Monstrelet, he had died proclaiming his intention to rebuild the walls of Jerusalem. In Henry's mind, there was a connection between Christian renewal and crusading; both, in their different ways, bore witness to the ideal of a united Christendom and the ruler's responsibility to promote that ideal.

The appreciation that rulers had of the Christian responsibilities of their office was a factor in the long after-life of crusading. Along with such other factors as the continued Muslim advance into Europe, it helped to ensure that princes like Charles V and Philip II were active in fighting the Infidel well into the 16th century. However – and here was the difficulty – the connection between crusading and public religion was simultaneously a factor in the decline of the movement. Crusading, to its disadvantage, became associated with a particular form of religion – Catholic religion: a connection reinforced by the pope's responsibility for authorising it. Once, as in Northern Europe, religion and spirituality began to run in different channels, crusading lost its appeal; indeed, from this time in the North it was condemned as an evil. English involvement in promoting crusade ended in the reign of Henry VIII. English experience of being a target of crusade began in his daughter's.

Nigel Saul is Reader in Medieval History at Royal Holloway, University of London. He is author of Richard II (Yale University Press, 1997).