Pope Saint Leo IV (847-855)

The pope who closed the breach opened in 846

The Saracen raid of 846 had revealed a dramatic weakness: the basilicas of Saint Peter and Saint Paul, lying outside the Aurelian Wall, could be plundered without the city of Rome itself being taken.^[5] For a 9th-century Christian, this was not a mere loss of treasure. It was the visible humiliation of the apostolic sanctuaries, of Peter's tomb and of the Roman liturgical heritage.

Leo IV was elected amid this fear. New Advent reports that the attack of 846 had left the Romans anxious for the safety of the city, and that this emergency explains his consecration without waiting for imperial authorisation.^[6] Treccani confirms that the difficult circumstances of the election caused a break with the procedure imposed by Lothair's ordinance: the Romans hesitated, but finally consecrated Leo on Easter Day 847, "without the prince's permission", while affirming that they did not wish to fail in imperial loyalty.^[7]

The founder of the Leonine City

Leo IV's most lasting act is the Vatican enclosure. In fewer than five years, between 847 and 852, he had the coastal defences repaired, the Aurelian Walls restored, and a fortified system built around the Vatican nucleus starting from Castel Sant'Angelo, defended by forty-four towers and opened notably by the Viridaria gate.^[8]

The new enclosure is not just a wall. It creates a civitas Leonina, a city named after its founder, able to protect Saint Peter's, pilgrims, monasteries and the quarters living around the apostolic sanctuary. Treccani stresses that this foundation, together with that of Leopolis near Civitavecchia, gives pontifical action an almost sovereign form: the pope orders the territory like a public power.^[9]

The coordinator of the victory of Ostia

In 849, a new Saracen fleet threatened Rome. The Liber Pontificalis recounts that God stirred the hearts of the men of Naples, Amalfi and Gaeta to fight alongside the Romans; their leaders came to the Lateran, declared they sought only victory against the pagans, then received communion from the pope's hands at Saint Aurea in Ostia.^[10]

Leo IV did not command a fleet like a modern admiral. He did something else: he verified the allies' intention, went to Ostia with an armed escort, celebrated Mass, prayed for the combatants, and gave the alliance an ecclesial form. In the pontifical narrative, the victory that followed is presented as the fruit of the protection of Peter and Paul as much as of naval manoeuvre.^[11]

A highly narrative Roman source

The Liber Pontificalis entry on Leo IV is exceptionally developed for the 9th century. Treccani notes that it contains a great quantity of news about Rome, its infrastructures and its churches, in the line of the entries on Leo III, Paschal I and Gregory IV.^[12]

This abundance is precious, but it requires careful reading. The text does not merely recount: it interprets. The storm of Ostia, the works, the gifts and the victory are presented as signs of divine mercy and of the pope's holiness. Its testimony must therefore be kept, while distinguishing facts, figures, liturgical gestures and the theology of the narrative.

The modern syntheses

New Advent gives an old but very useful Catholic synthesis: education at Saint Martin's, title of the Santi Quattro Coronati, consecration on 10 April 847, construction of the Leonine City, victory of Ostia, restoration of churches, crowning of Louis II, the Alfred dossier, synod of 853, Ravenna, Brittany and Constantinople.^[13]

Treccani supplies the critical complement: Leo IV appears as one of the popes who most clearly affirm the centrality of pontifical power in Roman society and in Latium; his "new cities" and his walls manifest an already mature jurisdictional sovereignty.^[14]

A Roman formed near Saint Peter's

Leo IV was born in Rome in the first decade of the 9th century, son of Radualdo according to Treccani, Radoald according to New Advent.^[15][16] His father's name could point to a Lombard family background settled in Rome, but Treccani warns that onomastics alone is not enough to prove a precise "ethnicity".^[17]

The future pope was educated in the monastery of Saint Martin in the Vatican, next to the basilica of Saint Peter.^[18][19] This formation explains part of his pontificate: the man who would fortify the Vatican grew up in contact with the sanctuary he would have to defend.

From the Santi Quattro Coronati to the See of Peter

Gregory IV noticed his pious conduct and made him subdeacon; Sergius II created him cardinal-priest of the title of the Santi Quattro Coronati, on the Caelian Hill.^[20] Treccani confirms this ecclesiastical career and stresses that Leo's personal qualities were recognised at a moment when Rome was seeking a shepherd able to answer the Saracen trauma.^[21]

The choice was swift, unanimous according to New Advent, and came about in a climate of general consensus.^[22][23] The speed was not a mere formality: it shows that the fear of 846 made a prolonged vacancy impossible.

A consecration without waiting for the emperor

Since the Constitutio Romana of 824 and Lothair's ordinance, pontifical consecration had to await a more binding imperial confirmation or presence. Sergius II died on 27 January 847; the Romans hesitated to consecrate Leo without imperial authority; but the danger was too great. On 10 April 847, Easter Day, they proceeded anyway.^[24]

The nuance is decisive: this was not a doctrinal revolt against the emperor. The pontifical biographer takes care to say that the Romans did not wish to fail in their obligations of loyalty.^[25] But the event reveals the tension of the century: Rome needed the Carolingians, without accepting that the sacramental life of the Church be paralysed by a political delay.

The trauma of the extramural basilicas

The Liber Pontificalis preserves the account of the 846 raid under Sergius II: a large fleet arrived near Ostia, seized the abandoned positions, then Saracen horsemen surprised Saint Peter's with "unspeakable iniquities".^[26] Even if the vocabulary is strongly polemical, the underlying fact is clear: the Vatican basilica lay outside the walls and was therefore exposed.

The catastrophe also revealed the inadequacy of the coastal defence. Gregoriopolis, fortified at Ostia by Gregory IV, did not suffice to prevent the enemy from using the sea and the Tiber as an avenue of threat.^[27]

Repairing the walls and towers

From the start of his pontificate, Leo IV put Rome in a state of defence. New Advent indicates that he repaired the walls of the city and entirely rebuilt fifteen great towers.^[28] Treccani broadens the picture: Leo restored the Aurelian Walls, strengthened Porto, created a new fortified settlement near Centumcellae, and also supported works at Orte and Amelia to control the Tiber valley.^[29]

This programme shows a geographical intelligence. Defending Saint Peter's was not enough; the maritime approaches, the coastline, the ports, the Tiber route, the hinterland cities and the monumental heart of Rome all had to be protected.

The Leonine City

The Vatican building site is the centre of the work. The new walls started from Castel Sant'Angelo and comprised forty-four towers, two posterns and one main gate. Treccani identifies the Viridaria gate, also called the Saint Peter or Saint Peregrine gate, as the entrance by which pilgrims coming from the Frankish route and the Via Triumphalis reached the sanctuary.^[30]

A metrical inscription, visible until the 15th century, named the city after its founder: civitas Leonina.^[31] The name is theologically speaking: the pope did not build a neutral quarter, but a city ordered around Peter.

The threat from the sea

The Liber Pontificalis places the new threat in the twelfth indiction, that is 848–849. The Saracens, remembering the profit of the previous raid, gathered near Sardinia and sought to reach the port of Rome.^[32]

The pontifical narrative stresses the fear of the Romans, but also the divine initiative: God stirred the men of Naples, Amalfi and Gaeta to fight with Rome.^[33] This reading does not erase the politics. It shows that Christian defence was conceived as an alliance of maritime cities, but blessed and ordered by the pope.

Naples, Amalfi, Gaeta and Rome

Before trusting the allies, Leo IV asked some of them to come to Rome to learn their intentions. Caesarius, son of Sergius, master of the soldiers of Naples, presented himself at the Lateran palace. The allies swore they came only to defeat the pagans with the Lord's help.^[34]

The pope received them, then went to Ostia with an armed escort. The Neapolitans prostrated themselves at his feet, asked to receive the Eucharist from his hands, and Leo celebrated Mass in the church of Saint Aurea.^[35]

Paraphrase — Before the pope, the allies swore they had come for no other reason than to win, with the Lord's help, victory over the pagans.^[36]

A victory read as a sign from God

The next day, the enemy fleet appeared off Ostia. The Neapolitans attacked; a violent wind rose, separated the fleets and scattered above all the Saracen ships.^[37] The Liber Pontificalis sees a miracle in it: God brought the wind out of His storehouse, preventing the enemies from doing harm.^[38]

New Advent sums up the battle more soberly: the Saracen fleet was completely destroyed off Ostia by the allied fleets of Rome, Naples, Amalfi and Gaeta, as well as by a storm.^[39] The two formulations do not contradict each other. The Catholic narrative can acknowledge the action of men, the weather and Providence without confusing them.

The prisoners at the Saint Peter's building site

The Liber Pontificalis reports that several survivors were brought alive to Rome; many were hanged from trees near the port of Rome, others kept in chains and employed on the wall begun around the church of Saint Peter or on other necessary works.^[40]

The detail is harsh, but historically telling. The victory of Ostia directly fed the building site of the Leonine City: the enemies who had wanted to plunder Peter became forced labour for fortifying his sanctuary. The pontifical reading sees a providential justice in it; the modern historian also sees the harshness of the 9th century.

A "new city" around Peter

Treccani insists on a major point: Leo IV did not merely repair walls; he gave form to new cities. The Leonine City around the Vatican and Leopolis near Civitavecchia received a name, an enclosure, a function and an urban rank.^[41]

This type of act takes up gestures associated with late Roman and proto-Byzantine imperial foundations: delimiting a circuit, inspecting the completed walls, distributing gifts, manifesting authority through the organisation of space.^[42] Leo IV thus acted as bishop of Rome, but also as the concrete holder of a territorial power.

Porto, the Corsicans and Leopolis

After the Roman works, Leo also rebuilt Porto and settled there Corsican exiles driven out by Saracen ravages.^[43] Treccani specifies that he had a new fortified settlement built in the hinterland of Centumcellae, a city devastated by the Saracens in 812.^[44]

These decisions show a policy of repopulation and defence. It was not only a matter of raising stones: inhabitants, communities, places of refuge and fortified points able to resist incursions were needed.

Latium framed by the dioceses

A pontifical document addressed to Bishop Virbonus of Tuscania redefined the boundaries of that diocese. Treccani sees in it a sign of the returning territorial role of episcopal sees in Latium, perhaps in connection with the administration of territories subject to pontifical sovereignty.^[45]

The point is discreet but important. In medieval Catholic thought, territory is not only military. It is also diocesan, liturgical, patrimonial and pastoral. Leo IV put walls in order, but jurisdictions too.

Saint Peter's, Saint Paul's and the wounded places

Leo IV sought to repair the damage of the 846 raid. New Advent notes that Saint Peter's had suffered greatly; even if the basilica never fully recovered its former magnificence, Leo made certain parts of it more beautiful than before.^[46]

He also restored Saint Martin's, where he had been formed, the Santi Quattro Coronati, of which he had been priest, the Lateran palace, the Anglo-Saxon quarter (burgus), Subiaco and many places in Rome and outside Rome.^[47]

The Santi Quattro Coronati

Treccani notes that the Santi Quattro Coronati received under Leo IV the greatest number of pontifical gifts among the churches cited in his entry. As the Carolingian enlargement of this church is often attributed to Gregory IV, this suggests that Leo was directly involved in completing or enriching the building site.^[48]

Leo also took care of the crypt and the relics beneath the ciborium (the canopy above the altar), a memory later preserved by an inscription of Paschal II.^[49] The builder pope was therefore not only an urban planner; he was a guardian of relics.

Santa Maria Nova and Saint Clement

New Advent attributes to Leo IV the construction of Santa Maria Nova, intended to replace Santa Maria Antiqua, threatened by the collapse of the Palace of the Caesars.^[50] Treccani also mentions interventions at Santa Maria in Trastevere, San Martino ai Monti and the preservation of a portrait of Leo IV in the fresco cycle of the lower church of Saint Clement.^[51]

Louis II crowned at Rome

In 850, Leo IV associated Louis II, son of Lothair, with the empire by imposing the imperial crown on him.^[52] Treccani notes that the Liber Pontificalis is curiously silent on this coronation, even though Louis II would subsequently be an important actor in relations between Rome, the Empire and the local clergy.^[53]

This silence is instructive. The relationship with the Carolingians was necessary, but not always peaceful. Lothair financially supported the Vatican walls; Louis II intervened in certain Roman dossiers; but Leo also defended his margin of autonomy.^[54]

The young Alfred of Wessex

Three years after the crowning of Louis II, in 853, Leo IV received at Rome the young prince Alfred of Wessex, aged about four. The Anglo-Saxon Chronicle (annal 853) reports that Æthelwulf sent his son Alfred to Rome, where Leo "consecrated him king and adopted him as his spiritual son"; Asser, in his Life of Alfred (ch. 8), specifies that the pope anointed the child as king, received him as an adopted son and confirmed him.^[55] A letter of Leo IV to Æthelwulf, printed in the Stubbs edition of William of Malmesbury (Gesta regum, vol. II, p. 42), adds that the pope invested Alfred, his godson, with the belt (cingulum) and the vestments of the consulship — a Roman honorific title; the authenticity of this letter, contested then readmitted (Nelson), remains debated among specialists.^[56] The gestures must therefore be distinguished: the sacramental confirmation (which made the pope the child's spiritual sponsor), the adoption as son and the consular investiture do not amount to a royal crowning — all the more so as in 853 Alfred, the youngest son, still had three elder brothers living. Modern historians see in it a confirmation accompanied by Roman honours, whose later accounts accentuated the royal reading; New Advent (Mann) keeps the high version of the old English tradition — royal anointing, confirmation, adoption, dismissal with the blessing of Saint Peter — taken here as such, illuminated by the contemporary dossier above.^[57][58]

Anastasius the Librarian

The long conflict with Anastasius, cardinal-priest of San Marcello, reveals a possible fracture within the Roman clergy. New Advent recalls that the synod of 853 condemned the refractory Anastasius.^[59] Treccani specifies that the latter, the future Anastasius the Librarian, was more or less openly supported by Louis II after his flight from Rome in 848, and that the emperor would try to impose him on the pontifical see after Leo's death.^[60]

The dossier shows that the question was not only moral. It opposed a line more open to the emperor's direct influence in Roman affairs and a line more concerned with pontifical autonomy, of which Leo IV was the centre.^[61]

Ravenna, Reims and Brittany

Leo IV also confronted Ravenna. New Advent reports that the rebellious conduct of John, archbishop of Ravenna, obliged the pope to travel to the city to recall respect for the law.^[62] Treccani adds that between 852 and 853, a pontifical legate sent to Lothair was assassinated in circles close to the archbishop; Leo went to Ravenna to arrest the culprits and bring them to Rome.^[63]

In Gaul, the dossier of Hincmar of Reims manifests another tension. Leo granted him the pallium in 847, extended certain usages in 851 at Lothair's request, but refused to give him a papal vicariate in Gaul that would have allowed him to judge other archbishops, bishops and abbots.^[64] In Brittany, he opposed the initiatives of Nominoë, who deposed bishops and created an autonomous ecclesiastical organisation around Dol.^[65]

Constantinople and Sicily

The Eastern dossier is less documented. New Advent reports that Leo IV refused to confirm the deposition of Gregory Asbestas, bishop of Syracuse, because Patriarch Ignatius had acted without Roman legates or letters.^[66] Even in opposition to the patriarch, Leo still had to defend himself against accusations of pro-Byzantine intrigues brought before Louis II; he refuted them, and the accuser Daniel was condemned to death, escaping the penalty only through the emperor's intercession.^[67] Marazzi, following the Life of Leo IV, reports for his part that the trial convened by the pope before Louis II — in which the official Daniel accused the superista Graziano of pro-Byzantine scheming — ended with the suspect's absolution.^[68]

These affairs show a pope placed between several pressures: the Byzantine East, the Carolingian Empire, Ravenna, the Frankish Churches, the maritime cities and the Roman factions. The greatness of Leo IV lies in the fact that he did not merely endure these forces: he coordinated them when they served Christian defence, and resisted them when they threatened Roman jurisdiction.

An important Roman synod

In 853, Leo IV held an important synod at Rome. New Advent indicates that he had various decrees adopted there for ecclesiastical discipline and learning, and that he condemned Anastasius, cardinal of San Marcello.^[69]

Leo IV did not merely build. He governed, judged, taught, corrected clerics and sought to raise formation.

Discipline as protection of the Church

In the context of the 9th century, discipline was not a secondary theme. An unruly clergy, over-autonomous metropolitans, arbitrarily deposed bishops, local powers manipulating ecclesiastical organisation: all this threatened the concrete freedom of the Church as much as the Saracens threatened its walls.

The coherence of the pontificate appears here. Leo protected Saint Peter's with stones; he also protected the Apostolic See with law. Walls without discipline would not have sufficed. Discipline without concrete defence would not have sufficed either.

Death and burial

Leo IV died at Rome on 17 July 855, shortly after the departure of Louis II.^[70] New Advent indicates that he was buried in Saint Peter's and that his name is found in the Roman Martyrology.^[71]

Treccani specifies that he was buried in the chapel where Leo I rested, which Leo IV had himself restored, together with the bodies of Leo II and Leo III.^[72] This burial symbolically unites four popes of the same name: Leo the Great, Leo II the pope of Constantinople III, Leo III the pope of Charlemagne, and Leo IV the defender of Peter's city.

A feast reported as suppressed, a name kept in the Martyrology

Leo IV's feast was celebrated on 17 July; Marazzi (2005) reports it as suppressed ("La festa di L. IV, ora soppressa"), though the calendar in force has not been rechecked for this article — only the entry in the Roman Martyrology (2004 edition) is cross-checked here.^[73] This does not remove his memory of holiness: the Roman Martyrology in force (2004 edition) still commemorates Saint Leo IV on 17 July as pope, defender of the City and promoter of Peter's primacy.^[74] New Advent already noted his presence in the Martyrology and states, in its own words, that he "is credited with being a worker of miracles both by his biographer and by the Patriarch Photius".^[75] As the Photian text invoked could not be located for this article, this double attribution rests here on Mann (1910) alone, cited as intermediary: the article does not present it as its own verification.^[76]

The attested facts must therefore be distinguished from the hagiographical reading: not every hagiographical trait should be turned into a probative dossier. But the Catholic reading must be kept: Leo IV was venerated as a saint because he was a vigilant shepherd, a man of prayer, a defender of Rome, a restorer of sanctuaries and a guardian of ecclesial law.

A holiness of protection

The holiness of Leo IV is not that of a withdrawn monk. It is a holiness of protection. He took a wounded city, a frightened people, profaned basilicas, a vulnerable coastline, divided clerics and competing powers; he made of them a programme of defence, restoration and government.

His pontificate teaches a simple truth: the supernatural does not dispense with building walls, organising alliances, administering goods, calling the undisciplined to order and protecting sanctuaries. At Ostia, Leo prays before the battle; at Rome, he has stones carried. In both cases, he acts as a shepherd.

• The old basilica of Saint Peter — the sanctuary Leo IV protected with the Leonine City.
• Pope Saint Leo III (795-816) — major Carolingian precedent and another great builder pope.
• Pope Saint Paschal I (817-824) — Carolingian Rome, relics and restoration of sanctuaries.
• Pope Benedict III (855-858) — immediate successor, elected by the clergy and people of Rome right after Leo IV's death, in the crisis opened by Anastasius: there is therefore no interregnum in which to insert "Pope Joan", a fable that appeared in the 13th century (Martin of Troppau's account placing her after Leo IV) and refuted by dates, coins and charters.^[89]
• The Papal States (756-1870) — the long framework of the popes' temporal and territorial power.
• The Saracen invasions of Italy — military context of the 846 raid and the battle of Ostia.
• The Carolingian papacy — the relationship between Rome, the Franks and the empire in the 9th century.