[1] Nothing is known with certainty about the history of the Augsburg Church during the centuries immediately following the collapse of Roman power in Germany and the turbulence of the great migrations, but it did survive.

There were short periods of rest, during which ecclesiastical life received a forward impulse, as, for instance, under Bishop Walther II Count Palatine von Dillingen (1133–52), under whom the possessions of the diocese were again consolidated and increased by his own inheritance; under Udalskalk (1184–1202), who with great ceremony placed the recently discovered bones of St. Ulrich in the new church of Sts.

These days of peace alternated with periods of conflict into which the Bishops of Augsburg were drawn, often against their will, in their capacity as Princes of the Empire, and the life of the Church accordingly suffered decline.

During the struggles between the popes and the emperors, Augsburg, like other large cities throughout the greater part of Germany, attained enormous wealth, owing to the industrial and commercial activity of the citizens.

New dissensions between the Prince-Bishop and the Free Imperial City arose under Burkhard von Ellerbach (1373–1404), whose accession was marked by grave discord growing out of the overthrow of the Patrizier, or aristocratic government, and the rise in municipal power of the crafts or guilds.

He worked with zeal and energy for the reformation of his diocese, held synods and made episcopal visitations in order to raise the decadent moral and intellectual life of the clergy; he restored the discipline and renewed the fallen splendor of many monasteries, canonries and collegiate churches.

Some members of its families, e.g. the Fuggers and the Welsers, were the greatest merchants of their time; they lent large sums of money to the emperors and princes of Germany, conducted the financial enterprises of the papacy, and even extended their operations to the newly discovered continent of America.

The city council however, set itself up in opposition, recalled (1531) the Protestant preachers who had been expatriated, suppressed Catholic services in all churches except the cathedral (1534), and in 1537 joined the Schmalkaldic League.

At the beginning of this year a decree of the council was made, forbidding everywhere the celebration of Mass, preaching, and all ecclesiastical ceremonies, and giving to the Catholic clergy the alternative of enrolling themselves anew as citizens or leaving the city.

An overwhelming majority of both secular and regular clergy chose banishment; the bishop withdrew with the cathedral chapter to Dillingen, whence he addressed to the pope and the emperor an appeal for the redress of his grievances.

In the city of Augsburg the Catholic churches were seized by Lutheran and Zwinglian preachers; at the command of the council pictures were removed, and at the instigation of Bucer and others a storm of popular iconoclasm followed, resulting in the destruction of many monuments of art and antiquity.

After the victory at Mühlberg (1547), however, the imperial troops marched against Augsburg, and the city was forced to beg for mercy, surrender twelve pieces of artillery, pay a fine, restore the greater number of churches to the Catholics and reimburse the diocese and the clergy for property confiscated.

Thus, after many perturbations and temporary restorations of the Catholic religion, the Protestants finally gained the upper hand in Württemberg, Oettingen, Neuburg, the Free Imperial Cities of Nördlingen, Memmingen, Kaufbeuren, Dinkelsbühl, Donauwörth, Ulm, in the ecclesiastical territory of Feuchtwangen and elsewhere.

Bishop Christopher von Stadion, while trying to protect Catholicism from the inroads of the Reformation, had sought to strengthen and revive ecclesiastical discipline, which had sadly declined, among both the secular and regular clergy.

By frequent visitations he sought to become familiar with existing evils, and by means of diocesan synods and a vigorous enforcement of measures against ignorant and dissolute clerics, secular and regular, he endeavored to remedy these conditions.

He advanced the cause of education by founding schools; he summoned the Jesuits to his diocese, among others Blessed Peter Canisius, who from 1549, in the capacity, of cathedral preacher, confessor, and catechist, exercised a remarkable fruitful and efficacious ministry.

Under Marquard II von Berg (1575–91) a pontifical boarding school (alumnatus) was founded in Dillingen, colleges were established by the Jesuits in Landsberg, and through the bounty of the Fugger family, in Augsburg (1580).

Heinrich von Knöringen, made bishop at the early age of twenty-eight, took especial interest in the university and the Seminary of Dillingen, both of which he enriched with many endowments; he convened several synods, converted Wolfgang, the Duke of Neuburg, to Catholicism,[contradictory] and during his long episcopate (1598–1646) reconciled many Protestant cities and parishes to the Catholic Church, being aided in a particular manner by the Jesuits, for whom he founded establishments in Neuburg, Memmingen, and Kaufbeuren.

By means of the Edict of Restitution of Emperor Ferdinand II (1629), vigorously and even too forcefully executed by the bishop, the Thirty Years' War first accomplished an almost complete restoration of the former possessions of the Diocese of Augsburg.

Owing to the losses suffered by the diocese on account of the treaty, a solemn protest was laid before the imperial chancery by Bishop Sigmund Francis, Archduke of Austria (1646–65).

Joseph, Landgrave of Hesse-Darmstadt (1740–68) exhumed with great ceremony the bones of St. Ulrich and instituted an investigation into the life of Crescentia Höss of Kaufbeuren, who died in the odour of sanctity.

The cathedral chapter, together with forty canonicates, forty-one benefices, nine colleges, twenty-five abbeys, thirty-four monasteries of the mendicant orders, and two convents were the victims of this act of secularization.