Frederick II , Duke of Austria Frederick II ( , 25 April 1211 – 15 June 1246 ) , known as Frederick the Quarrelsome ( ) , was the Duke of Austria and the Duke of Styria from 1230 to his death in 1246 . He was the fifth and last Duke of Austria from the House of Babenberg . Life . Frederick the Quarrelsome was born on 25 April 1211 , the second surviving son of Duke Leopold VI of Austria and Theodora Angelina , a Byzantine princess . The death of his elder brother Henry in 1228 made him the only heir to the Austrian and Styrian duchies . Two years later , his father died and Frederick succeeded him . His first spouse was Byzantine princess Sophia Laskarina , and his second wife was Agnes of Merania . Frederick called himself a " Lord of Carniola " . However , the couple divorced due to childlessness in 1243 . Frederick had no surviving children . Proud of his Byzantine descent , the young duke soon was known as " the Quarrelsome " because of his harsh rule and frequent wars against his neighbors , primarily with Hungary , Bavaria and Bohemia . Even the Austrian Kuenringer noble family , which had so far been faithful to the ruling house , started an insurgency as soon as his reign began . But most dangerous were his disputes with the Hohenstaufen Emperor Frederick II in the course of the rebellion of the emperor ' s son Henry ( VII ) , husband of Frederick ' s sister Margaret . Not only had the duke refused to appear at the 1232 Reichstag diet in Aquileia , appealing to the Austrian " Privilegium Minus " , and displeased the emperor by picking quarrels with King Béla IV of Hungary , he furthermore seemed to be involved in his brother - in - law Henry ' s conspiracy . When he again refused to attend the 1235 diet in Mainz , Emperor Frederick II finally ostracized him and gave permission to King Wenceslaus I of Bohemia to invade the Austrian lands . Vienna opened its gates for the united Bohemian and Bavarian forces and during the years of Frederick ' s ban became an imperial free city , where the emperor had his son Conrad IV elected King of the Romans in 1237 . However , the expelled duke managed to maintain his position as the ruler of an Austrian rump state at Wiener Neustadt . In 1239 , in a spectacular change in imperial politics , Duke Frederick became one of the emperor ' s most important allies . The conflict with Bohemia was settled by the engagement of his niece Gertrude of Babenberg with King Wenceslaus ' eldest son Margrave Vladislaus of Moravia . Negotiations with the emperor about the elevation of Vienna to a bishopric and of Austria ( including Styria ) to a kingdom were initiated , however , on condition that the duke ' s niece Gertrude now would have to marry the fifty - year - old emperor , who moreover had recently been banned by Pope Gregory IX and needed allies . In 1245 the terms were arranged , but the willful young girl , then in her late teens , refused to appear in the consummation ceremony at the diet of Verona . In the year before his death , Duke Frederick finally succeeded in gaining the March of Carniola from the Patriarchal State of Friuli , but upon his death it fell to the Carinthian duke Bernhard von Spanheim . Duke Frederick ' s ambitious plans were dashed when he died at the Battle of the Leitha River , in a border conflict he had picked with the Hungarian king Béla IV Árpád . He is buried at Heiligenkreuz Abbey . Legacy . As the last Babenberg duke , Frederick the Quarrelsome signifies the end of an era in the history of Austria . With his overambitious plans , which were frequently foiled by his erratic character , he somewhat resembled his later Habsburg successor Duke Rudolf IV . According to the 18th century historian Chrysostomus Hanthaler , Frederick was the first Austrian duke utilizing the red - white - red coat of arms after his accession — an attempt to prevail against the reluctant local nobles and to stress his autonomy towards Emperor Frederick II . The triband is first documented in a seal on a deed issued on 30 November 1230 , confirming the privileges of Lilienfeld Abbey . The medieval chronicler Jans der Enikel reports that the duke appeared in a red - white - red ceremonial dress at his 1232 accolade in the Vienna Schottenstift . As the Austrian " Privilegium Minus " also allowed women to inherit , his sister Margaret and his niece Gertrude would have been entitled to the throne . Shortly after the death of her uncle , Gertrude first married her fiancé Vladislaus of Moravia , who nevertheless died in the next year , then Margrave Herman VI of Baden , who did not manage to maintain his position in Austria , and finally in 1252 Prince Roman Danylovich , a younger brother of Kynaz Lev I Rurik , son - in - law of the Hungarian king . In the same year the Bohemian Přemyslid s made a second attempt to confirm their claims to Austria by arranging the marriage between Gertrude ' s aunt Margaret of Babenberg and King Wenceslaus ' son Ottokar II , more than twenty years her junior . Subsequently , Austria became of field of conflict between the Přemyslids and the Hungarian Árpád dynasty , in which Ottokar at first would prevail defeating King Béla at the 1260 Battle of Kressenbrunn , until finally being overthrown by the German king Rudolph of Habsburg at the Battle on the Marchfeld in 1278 .