Question: Fuelled by the earlier conflicts of Matthias Corvinus king of Hungary battled which empire during the Battle of Leitzersdorf?
Context: The Battle of Leitzersdorf was a battle between the Holy Roman Empire and the Kingdom of Hungary in 1484.  Fuelled by the earlier conflicts of Matthias Corvinus and Frederick III, Holy Roman Emperor it marked the end of anti-Ottoman preparations and initiations of a holy war.  It was the only open field battle of the Austro-Hungarian War, and the defeat meant – in long terms – the loss of the Archduchy of Austria for the Holy Roman Empire. The Hunyadi family was one of the most powerful noble families in the Kingdom of Hungary during the 15th century.  A member of the family, Matthias Corvinus, was King of Hungary from 1458 until 1490, King of Bohemia (ruling in Moravia, Lower Lusatia, Upper Lusatia, and Silesia) from 1469 until 1490, and Duke of Austria from 1487 until 1490.  His illegitimate son, John Corvinus, ruled the Duchy of Troppau from 1485 until 1501, and five further Silesian duchies, including Bytom, Głubczyce, Loslau, Racibórz, and Tost, from 1485 until 1490.  The Hunyadi coat-of-arms depicted a raven with a golden ring in its beak. The Peace of Olomouc was signed on 2 April 1479 between Matthias Corvinus of Hungary and King Vladislaus II of Bohemia (and Hungary, later), bringing the Bohemian War (1468-1478) to an end.  On 21 July 1479 the agreement was ratified during the course of festivities in Olomouc.  This treaty, overall, ratified all terms within the Treaty of Brno developed in March 1478 (with slight modifications made by the King of Hungary on 20 September 1478).  Based on the terms of the treaty, Vladislaus would cede the territories of Moravia, Silesia, and Lusatia to Corvinus.  If Matthias perished, then Vladislaus was permitted to redeem these lands for 400,000 florins.  Moreover, both monarchs would be permitted to utilize the title "King of Bohemia".  However, only Matthias was required to address the other claimant as the "King of Bohemia". The Treaty of Brno was a draft to the Peace of Olomouc developed in March 1478 in Brno by the envoys of Matthias Corvinus of Hungary and King Vladislaus II of Bohemia and Hungary in an effort to end the Bohemian War (1468-1478).  Corvinus accepted the accord and slightly modified it on 20 September 1478, which determined the division of Bohemian territories.  Based on the terms of the treaty, Vladislaus would cede the territories of Moravia, Silesia, and Lusatia to Cornivus.  If Matthias perished, then Vladislaus was permitted to redeem these lands for 400,000 florins.  Moreover, both monarchs would be permitted to utilize the title "King of Bohemia".  However, only Matthias was required to address the other claimant as the "King of Bohemia". The Siege of Vienna was a decisive siege of the Austrian–Hungarian War in 1485.  It was a consequence of the ongoing conflict between Frederick III and Matthias Corvinus.  The fall of Vienna meant its merging to Hungary from 1485 to 1490.  Matthias Corvinus also moved his royal court to the newly occupied city. Justina Szilágyi de Horogszeg (Hungarian: "horogszegi Szilágyi Jusztina" ; before 1455 – 1497) was a Hungarian noblewoman, who became the second wife of Vlad the Impaler, Voivode of Wallachia.  She was the daughter of Ladislaus or Osvát Szilágyi and thus a cousin of Matthias Corvinus, King of Hungary.  Corvinus first gave her in marriage to Wenceslas Pongrác of Szentmiklós.  Pongrác had inherited estates in Upper Hungary (present-day Slovakia), but was forced to renounce them in exchange for landed property he and Justina jointly received in Transylvania following their marriage.  After Pongrác died in 1474, the widowed Justina married Vlad, whom Corvinus acknowledged as the lawful voivode of Wallachia in 1475.  Vlad seized Wallachia in late 1476, but was soon murdered.  To strengthen her claim to her Transylvanian estates, she married Paul Suki, who was related to the former owners of those territories.  After the death of Suki, in 1479, Justina was married to John Erdélyi of Somkerék, until her death in 1497. The Bohemian War (1468–78) began when the Kingdom of Bohemia was invaded by the king of Hungary, Matthias Corvinus.  Matthias invaded with the pretext of returning Bohemia to Catholicism; at the time, it was ruled by the Hussite king, George of Poděbrad.  Matthias' invasion was largely successful, leading to his acquisition of the southern and eastern parts of the country.  Its core lands however, centered on Prague, were never taken.  Ultimately both Matthias and Poděbrad would proclaim themselves king, though neither ever acquired all the necessary subordinate titles.  When Poděbrad died in 1471, his successor Vladislaus II continued the fight against Matthias.  In 1478, the war ended following the treaties of Brno and the Olomouc.  Upon Matthias' death in 1490, Vladislaus would succeed him as king of both Hungary and Bohemia. Matthias Corvinus, also called Matthias I (Hungarian: "Hunyadi Mátyás" , Croatian: "Matija Korvin" , Romanian: "Matei Corvin" , Slovak: "Matej Korvín" , ; 23 February 1443 – 6 April 1490), was King of Hungary and Croatia from 1458 to 1490.  After conducting several military campaigns, he was elected King of Bohemia in 1469 and adopted the title Duke of Austria in 1487.  He was the son of John Hunyadi, Regent of Hungary, who died in 1456.  In 1457, Matthias was imprisoned along with his older brother, Ladislaus Hunyadi, on the orders of King Ladislaus V of Hungary.  Ladislaus Hunyadi was executed, causing a rebellion that forced King Ladislaus to flee Hungary.  After the King died unexpectedly, Matthias's uncle Michael Szilágyi persuaded the Estates to unanimously proclaim Matthias king on 24 January 1458.  He began his rule under his uncle's guardianship, but he took effective control of government within two weeks. Sigismund Ernuszt (Hungarian: "csáktornyai Ernuszt Zsigmond" ; 1445;– summer 1505) was Bishop of Pécs in the Kingdom of Hungary from 1473 to 1505.  Ernuszt was also Ban of Croatia, Dalmatia and Slavonia from 1494 to 1498.  He was the son of John Ernuszt, a converted Jew, who started his career as a custom's duty collector during the reign of Matthias Corvinus, King of Hungary.  Sigismund studied at the universities of Vienna and Ferrara in the early 1470s.  When the king made him bishop of Pécs, the Holy See confirmed him as the administrator of the diocese, but he was most probably never ordained bishop.  Matthias Corvinus also tasked him with the administration of the newly conquered Archduchy of Austria in 1486. Vladislaus II, also known as Vladislav II, Władysław II or Wladislas II (1 March 1456 – 13 March 1516; ; Hungarian: "II.  Ulászló" ; Polish: "Władysław II Jagiellończyk" ; Croatian: "Vladislav II.  Jagelović" ; Slovak: "Vladislav II.  Jagelovský" ), was King of Bohemia from 1471 to 1516, and King of Hungary and Croatia from 1490 to 1516.  As the eldest son of Casimir IV Jagiellon, he was expected to inherit Poland and Lithuania.  George of Poděbrady, the Hussite ruler of Bohemia, offered to make Vladislaus his heir in 1468.  Poděbrady needed Casimir IV's support against the rebellious Catholic noblemen and their ally, Matthias Corvinus, king of Hungary.  The Diet of Bohemia elected Vladislaus king after Poděbrady's death, but he could only rule Bohemia proper, because Matthias (whom the Catholic nobles had elected king) occupied Moravia, Silesia and Lusatia.  Vladislaus tried to reconquer the three provinces with his father's assistance, but Matthias repelled them.
Answer: Holy Roman Empire