Siege of Hainburg The Siege of Hainburg were two sieges of Hainburg conducted by Matthias I , King of Hungary , during the Austro - Hungarian War ( 1477 – 88 ) . The first siege was broken in July 1482 by the Imperial Army of the Holy Roman Empire . Corvinus laid siege to the town again in August 1482 , this time with better preparations , and took Hainburg in September 1482 . Background . Matthias I assisted Frederick III , Holy Roman Emperor , during the Bohemian Wars . Subsequently , relations deteriorated when Frederick III formed a Holy - Roman - Czech - Polish alliance in Nürnberg in 11 March 1474 against Hungary . A period of rearmament and mobilization in 1477 , followed by a short war , resulted in the Treaty of Korneoburg - Gmunden ; the treaty required the Holy Roman Empire to pay 100 , 000 florins of reparations to Hungary . However , the sum was never paid despite several warnings and delays . As tensions rose , both countries began looking for allies amongst the other ' s nobility . The situation was further inflamed by the defection of Johann Beckensloer , Archbishop of Esztergom in Hungary , to the Holy Roman Empire where he laid claim to the Archbishopry of Salzburg . He left Hungary on a feigned pilgrimage to Aachen ; the real reason was he was not in favor with the Gabriel Rangoni of Verona , the Bishop of Gyulafehérvár . Beckensloer took with him part of the Hungarian treasury he had access to , and lent it to Frederick III in exchange for Salzburg . The incumbent , Bernard II of Rohr , was convinced to step down , but Bernard II recanted and reasserted his claim the same year . The emperor had the canons of Salzburg ignore Bernard II ' s claim , who in turn sought the protection of Matthias I of Hungary on 18 November . On Bernard II ' s behalf , Hungary seized the properties of the archdiocese of Salzburg in Styria and Carinthia by the end of the year . Since the archdiocese was a secular - independent principality with holdings spread across the secular provinces , this did not mean war with the Empire . The Hungarian army confronted Imperial troops several times during the seizures . The ambiguous state of conflict led the Hungarians to occupy some Imperial castles , including Radkersburg , and resulted in the siege of Graz . Frederick III declared this a breach of the peace , but Matthias I replied Hungarian troops were entering territories belonging to Archbishop Bernard II , and were there on the archbishop ' s invitation . Furthermore , the Hungarian king reminded the Emperor of the outstanding reparations payment from the Treaty of Korneoburg - Gmunden , which entitled Hungary to collect the debt by other means . Finally , Matthias I accused the Empire of taking advantage of Hungary during the then - ongoing Ottoman – Hungarian Wars , using the southern deployment of the Hungarian army to violate Hungarian territory , including an attack on Győr that killed 800 civilians . In the spring of 1482 , Matthias I sent 4000 cavalry , led by Captain Johann Zeleny of Schonau , to plunder Austrian territory along the Danube up to Passau . The incursion was stopped by the intervention of Cardinal Antonio Caffarelli , Bishop of Ascoli , who organized a truce . Nonetheless , war was inevitable as both sides continued to strengthen their forces . First siege . On 4 July , Matthias I assembled an army at Köpcsény and departed for Hainburg . The castle was sited on a hilltop surrounded by the Danube ; the siege proceeded slowly due to the lack of siege weapons . The Empire deployed an army of 4000 troops , led by Ruprecht von Reichenberg , to lift the siege . Matthias I dispatched troops to determine the size and location of the relief force . The Hungarian scouts ran into the Imperial army at Rohrau , and launched a cavalry assault but were unable to break through the enemy ' s quadratic defense formation . The stiff resistance caused the Hungarians to begin retreating in disorder ; Hungarian captains Wilhelm Tettauer and Stefan Zápolya attempted to hold the line but were trapped with 70 other nobles by Imperial pursuers . The advance of the Imperial army forced Matthias I to lift the siege . The Hungarians abandoned their equipment and supplies as they retreated with all haste to Presburg . Zápolya was taken prisoner but managed to escape after drawing the sword of a custodian and using it to kill the custodian ; he rejoined the army at Presburg . The King of Hungary appealed to the nobility for reinforcements to join him at Presburg . Urban Dóczi , Bishop of Győr , raised 5000 troops in 50 days at his own expense . The Raci horsemen of Slavonia also responded . Learning from the first experience , siege engines were also added , including the " Varga - mortar " which required 80 horses to move . Second siege . The quick regeneration of the Hungarian army at Presburg allowed the Hungarians to seize the initiative and march against Hainburg . On 20 September , the Imperial army , now expanded to 10 , 000 troops , began the march back to lift the siege . Matthias I took 8000 troops , leaving the rest to maintain the siege , to attack the relief army . The Hungarians dug in after seeing the size of the enemy army , while the Imperial army prepared to send supplies into the town . During the lull both sides bombarded the other ' s outposts . An attempt by the Empire to sneak 42 wagons into Hainburg was foiled by Hungarian sentries . On 23 September , Prior Bartholomew Beriszló launched a surprise , and unauthorized , cavalry attack on Imperial positions ; this caused Imperial forces to abandon their fortifications and retreat with their wagons towards Bruck . Matthias I declined to pursue despite the urgings of several subordinates . Nonetheless , Francis Haraszti and Moses of Buzla led an unauthorized cavalry assault on the Imperial remnants ; Haraszti died from a shoulder cut and Moses was also wounded . All other attempts were forbidden . Matthias I returned to Hainburg to prosecute the siege . The town fell after a week of heavy bombardment . The defenders , led by Wolfgang Fuchs , agreed to surrender in exchange for 3000 florins and free passage . Taking the town had cost the King of Hungary 200 . 000 florins .