The events surrounding the union of Croatia and Hungary are the source of a major historical controversy.

Croatian historians argue that the union was a personal one in the form of a shared king, a view also accepted by a number of Hungarian historians, while some other Hungarian and Serbian historians insist that Croatia was conquered.

The significance of the debate lies in the Croatian claim to an unbroken heritage of historical statehood which is clearly compromised by the other claim.

The Hungarian claim was made in the 19th century during the Hungarian national reawakening, while the same argument could also be leveled about the idea of a personal union first articulated in the 14th century.

The actual nature of the relationship is inexplicable in modern terms because it varied from time to time.

Sometimes Croatia acted as an independent agent and at other times as a vassal of Hungary.

However, Croatia retained a large degree of internal independence.

The degree of Croatian autonomy fluctuates throughout the centuries as do its borders.