Mid 1849, in Northern Italy
The same day the Austrian army achieves a significant victory at Novara, a revolt breaks out further east in Brescia. With the bulk of Austrian forces engaged on the front, it falls to the other scattered forces in the area to restore order. On the third day, a small force arrives from Mantua to restore order, but is repulsed and driven back under heavy losses, including General Laval Nugent. By this time word had reached the city of the Piedmontese defeat at Novara, though local officials convinced the townspeople it is a false rumor spread by the Austrians to entice them to surrender.
After another week, a more significant force under General Julius Jacob von Haynau approaches the city after marching from Padua. Haynau threatens to burn the city to the ground if the city's leaders do not submit, which they furiously decline to do. Haynau commences a devastating bombardment of the city that brings the city to its knees after only two days. The leaders of the revolt are arrested and executed, troops are allowed to loot the town, and several notable landmarks are destroyed. The incident will ultimately go down infamously, as an example of mistreatment during Austrian administration in northern Italy.
Meanwhile, in the aftermath of his army's defeat, King Charles Albert had immediately pressed for peace once more, unwilling to see the Austrian army put his capital under siege. Radetzky's terms are harsh - Austrian garrisons are to be placed in Alessandria, Novara, and Genoa, and their surrounding jurisdictions placed under general Austrian occupation. The king is prepared to agree, his will to fight completely lost. His generals agree that continuing the war would be unwise, but are not convinced that the terms of the peace cannot be renegotiated more favorably. The Piedmontese government, on the other hand, is furious that the king is giving in so easily and there is outrage in Turin.
Responding to the tension, the King's son and heir apparent, Victor Emmanuel II, rushes to his father's war council to try and convince the king to renegotiate. Instead, the disgruntled generals quietly approach the Duke of Savoy and encourage him to take the necessary actions on his own, rather than ask his father for approval first. In the middle of the night at a farm just north of Novara, Radetzky meets Victor Emmanuel to discuss new terms. Radetzky has strict orders from the emperor to ensure the imposed peace is harsh enough to discourage the Piedmontese from meddling again any time soon, and the Field Marshal himself at first is not inclined to give in to any new demands.
From the outset Victor Emmanuel tries to distance himself from his father and the liberal government he has allowed to grow in power, and points out that it very well might take Austrian support to ensure he can successfully hold the throne if the liberals try to make a power grab. He promises he will do his best to curb the reach of the liberal government, and also that Piedmont-Sardinia will stay out of revolts and movements elsewhere in the Italian peninsula, including the Venetian and Roman republics. In turn, Austria will take only an indemnity from the kingdom and support Victor Emmanuel's accession to the throne, but will not enter his territory any further unless the government were to collapse. Neither party is overjoyed at the terms but both can live with them, and the armistice is concluded to be ratified officially by both parties in an expedient manner.
Upon his return to his father's camp, Victor Emmanuel relays the news of the new peace offer to the generals and to the ministers back in Turin, both of whom seem much relieved that the Duke has negotiated a better settlement. The liberals are not pleased that their new soon-to-be-king has granted tacit acquiescence to the destruction of the republican cause in Italy, but the moderates and conservatives alike agree that their kingdom is now not in a position to be the savior of all of Italy. Charles Albert agrees to abdicate quite willingly, indeed seeing this new option as in some way saving his honor rather than being humiliated by the terms he had originally agreed upon. The king would eventually take to exile in Portugal and die quietly a few years later.
With a peace concluded, the Piedmontese return to Turin where Victor Emmanuel can begin to take control of his government, while Radetzky moves the bulk of his forces away from the Piedmontese front to march on the revolutionaries of Tuscany. Posturing and bluster from both sides in the ensuing weeks almost results in a breakdown altogether of the peace, as Radetzky insists on keeping Austrian troops on Piedmontese territory until the agreement is formally signed, while Victor Emmanuel boasts that 50,000 Piedmontese troops will march once more into Austrian Lombardy. In the end, outside diplomatic channels convince both sides to back down.
The regime change and end to the conflict between Austria and Piedmont-Sardinia also means the Venetians have lost their chance to take any offensive. Austrian attentions will now be fully focused on the city's republic, and that makes Mazzini and his supporters exceedingly nervous, even as Manin continues to espouse confidence in the defenders of the city. At a solemn meeting of the city's assembly in April, Manin urges those gathered to support him in fighting on, hardened by the defeat at Novara and emboldened by the callous Austrian assault on Brescia. Mazzini's camp continues to make no headway in eroding Manin's dictatorial grip on the city, and plans are hastily formed to evacuate Mazzini from the city when such a measure becomes necessary.
It is into this climate of fear and uncertainty mixed with defiance that Haynau marches his forces, placed in charge of all Austrian operations against the city as a reward for his effective handling of the Brescia revolt until Radetzky's forces return from Tuscany. Though Austrian positions had already been regarrisoned in the weeks leading up to the renewal of the Piedmont war, no concerted offensive actions had been taken, nor had any sorties been launched from the city. That is about to change, as Haynau is determined to take the Venetian forward position at Marghera, where such a humiliating defeat had been inflicted months earlier.
A siege and bombardment of the fort begins in the last days of April, as the Austrians with far superior numbers are able to fan out and penetrate weak points from a multitude of directions. By mid-May the remaining Venetian defenders retreat back across the lagoon into the city proper; any other small remaining Venetian garrisons on the mainland will follow suit soon after as the Austrian army moves to begin bombardment of the city itself, aided by the small Austrian navy that now sits unopposed in the northern Adriatic, the Piedmontese navy having been compelled to withdraw as part of their peace deal.
With their control of the mainland slipping away and the city's resources increasingly limited and cut off, the mood in Venice begins to change significantly, especially as more and more news from elsewhere in Italy filters in, little of it positive for the republican cause.
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Author's Note: This update covers the northern theatre of Italy, part two later this week will cover events in Tuscany and Rome and such. As before, the butterflies here aren't doing too much yet, the one major difference from OTL is that it is Victor Emmanuel's impetus to get a better peace and 'force' his father to abdicate, whereas iOTL Charles Albert was himself an advocate of his own abdication (though this is all a bit muddled in the sources I am looking at, so perhaps I haven't written it too differently from OTL after all).
Methinks Mazzini being trapped in Venice spells bad news for the Italian nationalist movement...
Fun Fact: The siege of Venice saw the first air attack in human history. The Austrians dropped bombs from unmanned hot air balloons designed by Franz von Uchatius.
Balloons were used for reconnaissance before that though.
