Regicide and Rebellion
Gian Galeazzo's death did not immediately destabilize Italy. His prudent governance ensured an ample treasury and a loyal populace, and Gian Maria, still fresh from his victory in France, stood at the peak of his popularity; and in any event no man was foolish enough to revolt against the Iron Serpent, not with the realm at peace and the markets flourishing.
Emperor Sigismund of Germany
Germany had not intervened in Italy since the abortive expedition of King Rupert in 1404, and the ongoing civil war had prevented Sigismund from interceding in the Anjou-Visconti war. Now, however, he had secured the throne and dispossessed the rebellious Wenceslaus and Jobst of Bohemia and Moravia. King Sigismund of Hungary and Bohemia was thus crowned King of the Romans in Fritzlar on March 15th 1412, and immediately turned his sights to Italy. To become Emperor in full required a papal coronation, undertaken in 1414 with Visconti's blessing, but now that the great duke was dead Sigismund decided to test the waters once more.
Deft diplomacy might have forestalled a war, but Gian Maria was not his father. When Sigismund demanded that “Duke Gian Maria Visconti” appear before him the king flew into a rage, calling the Bohemian “A barbarian, a pygmy, a son of a harlot, not worthy of shoveling the stool of an illiterate German, and neither Roman nor Emperor nor king of Italy.” and summoned his army for war.
The fifty year old Sigismund was no fool. His body might be weakening but his mind was as sharp as ever- he had met Gian Maria in Milan during his 1414 procession, and readily noted the character and reputation of the Lombard heir. The insult given by his envoy was a very deliberate provocation, and before Gian Maria could muster his armies Sigismund swept through the Brenner Pass and into Italy itself. Gian Maria was forced to meet the Emperor's advance with whatever men he had near to hand.
The two armies met outside the small town of Lodi on June 28th, 1418. Gian Maria was a brilliant and experienced commander, and his men were confident and in good order, but the Hungarians were veterans of the endemic border warfare with the Turks. In a classic steppe tactic, the Magyar cavalry feigned retreat, and Gian Maria took the bait. The Hungarians promptly wheeled and routed the Italians, only the latter's good order “and the ferocious discipline of the Swiss” preventing a complete collapse of Gian Maria's army. Among the dead was the young Francesco Sforza, son of Muzio Sforza and himself a condotierri.[A]
Sigismund's soldiers, believing the battle won, promptly fell upon the Italian camp and spread out to loot the countryside. This proved a costly mistake: Gian Maria rallied his remaining soldiers and returned to the field, catching the disorganized Imperials off guard and routing them in turn. His own men, in a remarkable display of discipline, did not immediately loot the Hungarian camp as their enemies had; Gian Maria was a harsh disciplinarian, and maintained order among his men long enough to ensure the Imperials had truly fled. Only once he felt secure in his position did he turn to the loot, evenly and methodically dividing the spoils among his army and trusting his cavalry to guard the camp in the unlikely event that the Germans returned. Sigismund fell back to Verona in good order, but whatever plans he made for a further attack were immediately discarded when he received news of the revolt of the Bohemians, who on July 20th 1419 hurled King Sigismund's magistrates from the windows of the royal palace in Prague, thus beginning the Hussite Wars.
The death of Jan Hus three years prior was merely the latest in a long series of grievances against the Emperor. The Hussites- followers of Jan Hus- resented the emperor's high handed taxation; they resented also having their king, Wenceslaus, deposed, and the kingdom simply passed into the Emperor's hands with no respect for the traditional rights of the Bohemians to elect their own king. Sigismund had kept his boot firmly on the Bohemians' throats, but he erred in taking their silence for obedience and upon his departure across the Alps tensions finally boiled over. Hus' martyrdom and the Council of Bologna radicalized the Bohemians even as it polarized the Hussites themselves.
From the outset the Hussites had been divided from the more moderate Ultraquists or Calixtines, and the militant Taborites, so named for their home city. The moderate Ultraquists, although equally harsh in denouncing Hus' murder, insisted that “with his martyrdom he won the Church her salvation” and claimed that he had been murdered not by the Pope but by either Emperor Sigismund or “the Serpent of Milan” depending on their politics; the radical Taborites on the other hand rejected the Council of Bologna almost entirely as “stained with martyr's blood” and insisted in the complete abolition of the Catholic Church of Bohemia. The major doctrinal heresy of the Ultraquists was their insistence that both bread and wine be served to the laity; at the time it was customary among Catholics for only the priests to drink the Eucharist wine. More generally they advocated church reform to eliminate secular corruption from the Church administration, and the Council of Bologna itself was very well received among them.
In contrast to the Ultraquists the radical Taborites called for “no more lords and servants”, an end to all taxation and the collectivization of all private property (especially land), and a return to the “pure and innocent” state of the early church. Empowered by the gold mines of Tabor- their stronghold- the Taborites created a communal, egalitarian society of peasants, preachers, and citizens. They abided by a puritanical discipline, and elected the formidable Jan Zizka as one of their leaders.
Statue of Jan Zizka, Prague
Jan Zizka's innovative and unconventional tactics and skilled use of terrain mark him as the greatest military commander of his era. “The One Eyed Dragon of Bohemia” drilled his soldiers in powerful infantry tactics, utilizing the Hussites' famous wagon forts and Europe's first widespread use of field artillery and massed musket fire to overcome the much more numerous Imperial armies opposing him. Hussite War wagons typically had around twenty soldiers, split evenly between gunners and crossbowmen on the one hand and men armed with pikes and maces on the other. The typical tactic was to deploy defensively, goad the enemy into attacking via artillery bombardment, and then counterattack after beating off the assault. The Hussites' guns proved especially devastating at close range, and slaughtered hundreds of German and Hungarian knights.
On the 22nd of December 1421 Jan Sizka and roughly ten thousand followers were encircled and besieged an Imperial army eight times their size at the Battle of Kutna Hora. Although Hussite artillery blunted the Imperial attacks Sigismund felt confident in his eventual victory. Zizka, however, proved Sigismund's overconfidence when he ordered a general attack. The Hussites grouped into armored columns, and under heavy artillery support Zizka punched a hole in the Imperial lines and escaped with his forces into the Bohemian countryside.
the Battle of Kutna Hora
Gian Maria did not wait idly for Sigismund's return. In Milan he raised fresh forces, and in the winter of 1421 his envoy arrived in the Palazzo Ducale in the Republic of Venice proposing a joint offensive against the Empire.
The Republic of St Mark needed little encouragement. Venice had a centuries-running conflict with Hungary over Dalmatia, and Sigismund had additionally supported the cities of Friuli against the Republic. Doge Tomasso Mosenigo was offered not only the Patriarchate of Aquileia but “all the cities and lands [belonging to Sigismund] along the Adriatic Coast.”
The Republic readily agreed and launched an invasion of Aquileia. The cities of Friuli despised the rule of the Patriarch and readily submitted to the Republic's rule, and by March 9th the Venetians were across the Izonso. Trieste was besieged by land and sea on March 14th, and after defeating a Habsburg relief army on April 24th the city finally fell on June 1st, 1422, the banner of St Mark raised above its walls by the victorious Venetians.
The sheer effrontery of the Italian invasion and the lingering menace of a Polish intervention finally convinced Sigismund to negotiate with the rebels. On July 22nd, 1422 he met with the moderate Ultraquists to discuss terms. The Hussites reiterated the demands made in the Four Articles of Prague- freedom of worship, acceptance of a dual communion, expropriation of all church property, and punishment for mortal sins, especially prostitutes which were singled out.
The Papal Legate present in Sigismund's camp steadfastly opposed any reconciliation with the heretics whatsoever and threatened excommunication for attempting to do so, but Sigismund by now viewed the Church as a mere instrument of the Italians, and largely ignored the Pope's threats. By the Peace of 1422 the Four Articles of Prague were largely accepted, in modified form:[b*]
the right of the Hussites to use communion “in both kinds” ie with wine and bread;
general tolerance of the Ultraquist Church, on condition of a personal oath of loyalty of all its members to King Sigismund himself;
Royal veto power over the appointment of Bohemian clergy;
the subordination of the clergy and their courts to the king and his magistrates;
the reduction (but not elimination) of existing Church estates and an end to their tax privileges;
The Bohemian revolt thereafter rapidly drew to a close. Tabor itself was besieged and taken by a combined Ultraquist-Imperial army, and Jan Ziska and what remained of his followers forced to flee to Poland. With Bohemia pacified Sigismund departed for Italy with the bulk of his army, leaving behind his lieutenants to finish sweeping up the remnants of the rebels.
Gian Maria anticipated Sigismund's return, however, and as the Germans were crossing through the Brenner Pass they were assailed “by a great force of fierce Italians.” The Germans were routed, and in the chaos Emperor Sigismund himself was wounded and taken prisoner.
What followed next is disputed. German sources claim that Gian Maria struck down the Emperor “in a rabid rage.” Italian sources give a different end to the Emperor: upon being brought before him, Gian Maria exclaimed, “You call yourself King of the Romans, but the Romans deposed their tyrants and destroyed them,” before beheading Sigismund “with a single stroke of his sword” and vowing to mount the corpse above the gates of the royal palace of Fritzlar.
If there is any truth to the Italian account then there was method to Gian Maria's madness: with Sigismund died the House of Luxemburg, which had ruled Germany for almost seven decades. Bohemia already smoldering in rebelliousness against the Empire; Gian Maria may have perceived that, with a single (literal) stroke, he might destroy Germany's fragile peace and plunge his northern neighbor into the same sort of internecine squabbling that he had so ruthlessly exploited in France. He was not alone on his designs on Imperial territory- to the west, the powerful duke John of Burgundy desired the rich lands of Alsace, Luxemburg, and Metz, while to the east Poland rallied once more to the aid of the Hussites.
In 1410 the Wolf of Lombardy taught the French to fear his name. Now, more than a decade later, he intended to give the same lesson to Germany.
[A]For those who don't know, the 1444 Peace of Lodi OTL was a masterpiece of diplomacy by none other than Francesco Sforza, the condotierri captain who married Filippo Maria's bastard daughter and claimed his duchy after the Visconti's extinction and among the general chaos of the Ambrosian Republic. Killing him at Lodi was a trans-timeline irony I simply couldn't resist.
[B*]This is a major divergence over OTL, where Sigismund refused to compromise at the behest of the Papacy. TTL, however, the Hussites (and reform in general) received a veneer of respectability from Bologna, and the subordination of Rome means Sigismund doesn't trust the Pope to have his best interests in mind, not when Gian Maria is ravaging the Austrian countryside.