With the aid of John, burgrave of Montfoort, who had been called in, after the manner of the Italian podestas, and endowed with supreme power for the defence of the town, the Utrechters defeated all the efforts of their bishop, aided by the Hollanders and an aristocratic faction.
In June 1158 Frederick set out upon his second Italian expedition, which was signalized by the establishment of imperial officers called podestas in the cities of northern Italy, the revolt and capture of Milan, and the beginning of the long struggle with pope Alexander III., who excommunicated the emperor on the 2nd of March 1160.
A further visit to Italy in 1163 saw his plans for the conquest of Sicily checked by the formation of a powerful league against him, brought together mainly by the exactions of the podestas and the enforcement of the rights declared by the doctors of Bologna.
Although the emperor's experiment was short-lived podestas soon became general in northern Italy, making their appearance in most communes about 1200.
There were, moreover, podestas in some of the cities of Provence.
Gradually the podestas became more despotic and more corrupt, and sometimes a special official was appointed to hear complaints against them; in the 13th century in Florence and some other cities a capitano del popolo was chosen to look after the interests of the lower classes.
In other ways also the power of the podestas was reduced; they were confined more and more to judicial functions until they disappeared early in the 16th century.
The example of Italy in the matter of podestas was sometimes followed by cities and republics in northern Europe in the middle ages, notably by such as had trade relations with Italy.
The podestas of some Italian towns, but more especially to the heads of the universities, the representatives and rulers of the universitas magistrorum et scholarium, elected usually for a very short time.