The early 15th century was one of last brief but impactful periods of crisis that characterized political change in Northern Italy before the Italian States would be subjected to the coercion of to the emergent nation-states of Europe and their respective Empires. Thus the first decade of the 15th century would see the balance of power, and even the social contract, tied to governance and rule of law in large parts of Italy change significantly, greatly to the benefit of the Republic of Venice.

Indeed, the Patriarch of Aquileia was not the only polity affected by this crisis in the 15th century. The political system in vogue in Italy, that is to say convoluted mechanisms of collegiate governance centered on urban communities, had been in distress for the greater part of the previous century. Factional infighting both within important cities and in their satellite communities had led to the emergence of political dynasties willing and able to subvert collegiate government and eliminate opposition by force of arms. These dynasties exploited the legal constructs and political winds of "The Empire" to further their own legitimacy, while the emergent Bavarian, Bohemian, and Austrian polities were themselves locked in a struggle for hegemony across the Alps and hungry for acknowledgement and support in Italy. By the end of the century, two great dynasties had assembled polities able to challenge for hegemony across the peninsula: the Visconti of Milan and the Scaligeri of Verona.

The conflict between the Milanese and Veronese states has important implications for Venice, which in the 14th century was still a state governing a collection of communities in and around its eponymous lagoon: the Rialtine Islands, the islands of Burano, Murano, Torcello, Malamocco and Pelestrina, as well as the community and lagoon of Eraclea immediately to the north separated from Venice by the sediment of the Piave River estuary. To this, we can add a collection of communities across the Adriatic Sea on the Istrian Peninsula and along Dalmatian coast, associated with Venice by treaties ranging from guarantees of protection to agreements of subjugation, as well as a number of islands and concessions in the Agean Sea granted by the Eastern Empire.

The Venetian state was thus almost an exclusively a maritime one, whose presence on the Italian mainland was limited to a handful of watch-towers and outposts along the navigable rivers flowing into the lagoon. And it was this lack of presence on the mainland, coupled with the republic's immense wealth and resources, that would make Venice a trusted political partner. Indeed, the Venetian governing class' attitude to conflicts in Italy had historically been one of guarded indifference. Rather than organizing expeditions to subjugate weaker neighbors, far more energy was spent in contesting simpler and more practical things like the rights to the salt marshes in the southern lagoon. Indeed, rights to harvest salt was a frequent point of contention with the nearby city of Padua, especially once the Paduan political system was subverted by the wily Carrarese dynasty who would themselves eventually submit to the Scaligeri of Verona.

Also unlike peers of similar size and prosperity, the Venetian state retained its largely collegiate government. Indeed, the only serious attempt at usurpation in its history had been caused by a small clique of minor aristocrats, whose attempt at armed uprising was subdued over the course of a few hours.

So Venice's prosperous and enfranchised aristocracy, with social and economic ties entrenched in Northeast Italy and no reputation for warmongering, made the Republic an appealing overlord following the destructive and convoluted decades-long conflict by which Milan eliminated Verona as a contender in Northern Italy. While Milan and Venice had conspired together to cause the downfall of Verona (Venice even making one of its first large-scale commitments to military action) the Milanese had originally taken the lead in terms of territorial gains. However, the natural instability tied to the nature of dynastic control in collegiate systems of government, in this case augmented by the premature death of the Milanese strongman Gian Galeazzo Visconti, quickly led to a vicious armed struggle for control of Lombardy and rapid action by the northeastern cities to request protection from the Republic.

Thus by the early 15th century the Venetian governing class was brimming with confidence. The ruling councils of new subjects on the Italian mainland were eager to garner favor by committing resources to common initiatives, while the Republic's natural rival, Milan, was still being torn apart by internal strife. It is in this mood that we arrive at the subjugation of the Prince-Bishopric of Aquileia.

The Republic's relationship with its northern neighbor had been characterized by serious contrasts from the very start. Already in their earliest history the Venetians were in competition with the great city to the north, which had been one of the late Roman Empire's most important urban centers. By the second and third iterations of the Kingdom of Italy, the city's fates were already divergent and contrasting: Aquileia, although already diminished in influence, nonetheless stood with Cividale and Udine as one of the urban and political centers which would allow the Margrave of Friuli the resources to be one of the most influential political actors in Italy, while Venice would instead foster strong ties with the Eastern Empire, itself locked in systemic conflict with the emergent Italian state. By the eighth century, the conflicting spheres of military control and political influence in the northeast had led the Byzantine military government seated in Ravenna to appoint a patriarch in the coastal outpost of Grado in order to directly oppose the influential ecclesiastical seat of Aquileia. Even as the Byzantines were driven out of Italy the Venetians would remain in the ecclesiastical province of Grado, casting an uncomfortable and lasting shadow on Aquileia's prestige.

Not that the Venetians were much interested in submitting to Grado's authority either, be it spiritual or otherwise. While in the rest of Italy political and religious authority was very much entwined, the communities on the Venetian lagoon could be aggressively anticlerical. Of course, in Venice as elsewhere religion was an important part of everyday life (as well as an important component of political legitimacy and governance) but the Venetians in the ninth century were also not averse to occasionally sailing up to Grado to throw an uncooperative Patriarch off a tower. This was a much different relationship than that which was developing in the rest of Italy, where religious figures played a central role in delegating and organizing political authority at least until the early thirteenth century. Indeed, Venice's antagonistic relationship with religious authority would be a hallmark of its political line (only in 1516 would the Republic's government agree to no longer interfere in clerical appointments).

All this is to express on the one hand how much the Venetians might have cared about the eleventh-century investiture of religious figures with broad and official temporal authority (not very much) and on the other hand that the investiture of political authority in the Patriarch of Aquileia was both unsurprising in its inception but ultimately a demonstration of the region's decline and weakness in its longevity. Indeed, while the German Emperor Otto would attempt definitively unite the German and Italian political systems, his unsuccessful but formidable effort immensely empowered the urban clergy of Italy. This would lead to the growth of an elaborate and autonomous political system in Lombardy (where Milan is), while it is telling that no similarly elaborate system developed in the Friuli (where Aquileia is) ultimately retaining the Patriarch as the principal authority.

This is the Aquileia we encounter at the start of the fifteenth century: a political dinosaur from a bygone era, formerly an important city of the Roman Empire, but now not even the most important center of a peripheral region in Italy in spite of its political and religious importance. Indeed, the Patriarch's temporal control had been eroding for centuries, as his coastal towns had all defected to the Republic, while the patricians of his most important inland cities (Cividale and Udine) were not only also developing increasingly close social and economic ties with the Venetians but themselves vying for influence within the Patriarchate in contests increasingly likely to degenerate into armed confrontations. If the Patriarch's temporal authority had not yet been challenged by some other Italian rival, it was probably because there were more appetizing pickings closer to the heart of the peninsula.

Thus in 1419, the Venetian Republic campaigned to occupy the Patriarchate's major cities and end the Patriarch's temporal authority. It is probable that the Venetian government was alarmed by the presence of Austrian backers of various armed factions in the Friuli, and the Venetians were also eager to stake out a clear border between their powerful neighbor to the north and their newly expanded state on the Italian Mainland. It is ultimately telling that Venice's own forces seizing control of the Friuli would be led and supplemented by a faction Udinese aristocrats.