Second civil war
The next revolt occurred a mere two years later, in 832. The disaffected Pepin was summoned to his father's court, where he was so poorly received he left against his father's orders. Immediately, fearing that Pepin would be stirred up to revolt by his nobles and desiring to reform his morals, Louis the Pious summoned all his forces to meet in Aquitaine in preparation of an uprising, but Louis the German garnered an army of Slav allies and conquered Swabia before the emperor could react. Once again the elder Louis divided his vast realm. At Jonac, he declared Charles king of Aquitaine and deprived Pepin (he was less harsh with the younger Louis), restoring the whole rest of the empire to Lothair, not yet involved in the civil war. Lothair was, however, interested in usurping his father's authority. His ministers had been in contact with Pepin and may have convinced him and Louis the German to rebel, promising him Alemannia, the kingdom of Charles.
Soon Lothair, with the support of Pope Gregory IV, whom he had confirmed in office without his father's support, joined the revolt in 833. While Louis was at Worms gathering a new force, Lothair marched north. Louis marched south. The armies met on the plains of the Rothfeld. There, Gregory met the emperor and may have tried to sow dissension amongst his ranks. Soon much of Louis's army had evaporated before his eyes, and he ordered his few remaining followers to go, because "it would be a pity if any man lost his life or limb on my account." The resigned emperor was taken to Saint-Médard de Soissons, his son Charles to Prüm, and the queen to Tortona. The despicable show of disloyalty and disingenuousness earned the site the name Field of Lies, or Lügenfeld, or Campus Mendacii, ubi plurimorum fidelitas exstincta est.
On 13 November 833, Ebbo, with Agobard of Lyon, presided over a synod at the Church of Saint Medard in Soissons which saw Louis undertake public penance for the second time in his reign. The penitential ritual that was undertaken began when Louis arrived at the church and confessed multiple times to the crimes levied against him. The crimes had been historic and recent, with accusations of oath breaking, violation of the public peace and inability to control his adulterous wife, Judith of Bavaria. Afterwards, he threw his sword belt at the base of the altar and received judgement through the imposition of the hands of the bishops. Louis was to live the rest of his life as a penitent, never to hold office again. The penance divided the aristocracy. The anonymous biographer of the Vita Hludovici criticized the whole affair on the basis that God does not judge twice for sins committed and confessed. Lothair's allies were generously compensated. Ebbo himself received the monastery of St Vaast whilst Pepin was allowed to keep the lands reclaimed from his father.
Men like Rabanus Maurus, Louis's younger half-brothers Drogo and Hugh, and Emma, Judith's sister and Louis the German's new wife, worked on the younger Louis to make peace with his father, for the sake of unity of the empire. The humiliation to which Louis was then subjected at Notre Dame in Compiègne turned the loyal barons of Austrasia and Saxony against Lothair, and the usurper fled to Burgundy, skirmishing with loyalists near Chalon-sur-Saône. Louis was restored the next year, on 1 March 834.
On Lothair's return to Italy, Wala, Jesse and Matfrid, formerly count of Orléans, died of a pestilence. On 2 February 835 at the palace Thionville, Louis presided over a general council to deal with the events of the previous year. Known as the Synod of Thionville, Louis himself was reinvested with his ancestral garb and the crown, symbols of Carolingian rulership. Furthermore, the penance of 833 was officially reversed and Archbishop Ebbo officially resigned after confessing to a capital crime, whilst Agobard of Lyon and Bartholmew, Archbishop of Narbonne were also deposed. Later that year Lothair fell ill; once again the events turned in Louis favour.
In 836, however, the family made peace and Louis restored Pepin and Louis, deprived Lothair of all save Italy, and gave it to Charles in a new division, given at the diet of Crémieu. At about that time, the Vikings terrorized and sacked Utrecht and Antwerp. In 837, they went up the Rhine as far as Nijmegen, and their king, Rorik, demanded the weregild of some of his followers killed on previous expeditions before Louis the Pious mustered a massive force and marched against them. They fled, but it would not be the last time they harried the northern coasts. In 838, they even claimed sovereignty over Frisia, but a treaty was confirmed between them and the Franks in 839. Louis the Pious ordered the construction of a North Sea fleet and the sending of missi dominici into Frisia to establish Frankish sovereignty there.