During the Investiture Controversy of 1077, King Henry IV of Germany deposed the Veronese margrave Duke Berthold II of Carinthia, as he had sided with antiking Rudolf of Rheinfelden.

On 3 April 1077 at Pavia Henry, on his way back from the Walk to Canossa, vested Patriarch Sieghard of Beilstein with immediate comital rights in the Friulian lands of Verona, raising him to the status of a Prince-Bishop.

Back in Germany, King Henry in addition nominally assigned the suzerainty over the marches of Carniola and Istria to the patriarchs as ecclesiastical Princes of the Holy Roman Empire.

The act, traditionally regarded as the birth of the ecclesiastical state of Aquileia, led to a long-running conflict with the rivaling margraves from the Carinthian House of Sponheim and the Andechs dukes of Merania.

In 1186 Patriarch Godfrey crowned Frederick Barbarossa's son, Henry VI, as King of Italy: in retaliation, Pope Urban III deposed him.

Their autonomy was strengthened, when they inherited the Imperial County of Tyrol in 1253 and were elevated to Princes of the Holy Roman Empire by Emperor Charles IV in 1365.

The capital of the state was moved first to Cividale and then, from 1238, to Udine in central Friuli, which had been a favourite residence of the patriarch since the 13th century and soon became a large city.

However, they had to cope with the rising naval power of the Republic of Venice, which in the late 13th century had occupied the western Istrian coast from Capodistria (Koper) down to Rovigno (Rovinj).

In the late century the patriarchate had to face the increasing rivalry with Venice, as well as the inner strifes between its vassals, and also became entangled in the endless wars between Guelphs and Ghibellines.

In the December of that year an Imperial army captured Udine and, in the following January, Louis of Teck was implemented as patriarch in the city's cathedral.

Doge Francesco Foscari in 1433 signed an agreement with Emperor Sigismund, whereby the Empire ceded the Domini di Terraferma, stretching from the Adriatic Sea to the Alps, to the Republic, then officially as an Imperial fief.

In 1445, after Patriarch Ludovico Trevisan at the Council of Florence had acquiesced in the loss of his ancient temporal estate in return for an annual salary of 5,000 ducats allowed him from the Venetian treasury, the war could be considered really over.

The former Friulian state was incorporated in the Venetian Republic with the name of Patria del Friuli, ruled by a General Proveditor or a Luogotenente living in Udine.

[3] The parliament cooperated with the patriarch in treating with foreign powers, but it had no role in the Venetian conquest and incorporation of Friuli into the Domini di Terraferma in 1420.