Besides a diocese formed from those of Bremen and Verden, the new metropolitan was to have the right to send missions into all the northern lands and to consecrate bishops for them. Ansgar was consecrated in November, 831, and, the arrangements having been at once approved by Gregory IV, went to Rome to receive the pallium directly at the hands of the pope and to be named legate for the northern lands. This commission had previously been bestowed upon Ebbo, Archbishop of Reims; but an amicable agreement was reached by which the jurisdiction was divided, Ebbo retaining Sweden for himself. For a time Ansgar devoted himself to the needs of his own diocese, which was still missionary territory with but a few churches. He founded in Hamburg a monastery and a school; the latter was to serve the Danish mission, but accomplished little. The 830s and 840s were a successful time for Ansgar despite the difficulties in the Empire at this time which involved Ansgar losing Turholt due to the division of Louis’ empire after 840. He was to face difficulties in his career when Hamburg was unexpectedly sacked in 845, effectively reducing the church’s treasures and books to nothing and leaving the entire diocese completely destroyed and deemed unrestoreable. Therefore, Ansgar was given the bishopric in Bremen in 847, but this was inappropriate as Hamburg had been an archbishopric. Thus, Bremen and Hamburg were combined for Ansgar, which caused great consternation and hostility from the bishops of Cologne to whom Bremen had been subject. This issue was not resolved in Ansgar’s favor until 864 by Pope Nicolas I. Through all this political turmoil, Ansgar continued his mission to the northern lands and reviving the mission to Sweden in 850. Times were difficult during the Danish civil war and Ansgar was forced to establish good relations with two kings, Horic the Elder and his son, Horic II. Both were receptive to his mission and collaborated with him until Ansgar’s death in 865 (Wood, 124-125).
After the death of Louis the Pious (840), Ansgar lost the abbey of Turholt, which had been given as an endowment for his work, and in 845 Hamburg was destroyed by the Danes, so that he was a bishop without either see or revenue. Many of his helpers deserted him, and his work was in danger of extinction. The new king, Louis the German, came to his aid; after failing to recover Turholt for him, he planned to bestow upon him the vacant diocese of Bremen. There were many canonical and other difficulties in the way; but after prolonged negotiations Pope Nicholas I approved the union of the two dioceses (864).
From 848 Ansgar resided in Bremen, and did what he could to revive the Danish mission. When he was established in a position of dignity once more, he succeeded in gaining permission from King Haarik to build a church in Sleswick, and secured the recognition of Christianity as a tolerated religion. He did not forget the Swedish mission, and spent two years there in person (848-850), at the critical moment when a pagan reaction was threatened, which he succeeded in averting.
In 854 Ansgar returned to Sweden. Now a king Olof ruled in Birka. According to Rimbert, he was well disposed to Christianity. On a Viking raid to Apuole in Kurland, the Swedes prayed, and with God's help they plundered the Curonians.
Ansgar died 865 in Bremen.
Through the course of this work, there are many important junctures in his life that are embarked on after a vision has occurred to Ansgar. His early studies were inspired by a vision of his mother in the presence of Saint Mary, and Rimbert states that Ansgar’s ensuing devotion to the acetic life of a monk. When the Swedish people were left without a priest for some time, he begs King Horic (of the Swedes) to help him with this problem. After receiving his consent, he consults with Bishop Gautbert to find a suitable man. The two together sought the approval of King Louis, which was granted when he learned that they were in agreement on the issue. Ansgar was convinced he was commanded by heaven to undertake this mission, and he was influenced by a vision he received. In his vision, Ansgar was concerned about the journey. In it, he saw buildings of different kinds and in one of them he met a man who reassured him of his purpose and informed him of a prophet that he would meet, the abbot Adalhard, who would instruct him in what was to happen. In his vision, he searches for and finds Adalhard who commands "Islands, listen to me, pay attention, remotest peoples" which Ansgar interprets as God’s will that he go to the Scandinavian countries as "…most of that country consisted of islands, and also when, 'I will make you the light of the nations so that my salvation may reach to the ends of the earth,' was added, since the end of the world in the north was in Swedish territory" (Life of Ansgar, 17-18).
Statues dedicated to him stand in Hamburg and Copenhagen as well as a stone cross at Birka. A crater on the Moon, Ansgarius, has been named for him. Ansgar is the patron saint of Denmark. His feast day is 3 February.