Front Palace (Thai: วังหน้า "wang na" ) is the colloquial name for the residence, person and office of Krom Phra Rajawang Bovorn Sathan Mongkol (กรมพระราชวังบวรสถานมงคล pronunciation), which was the Siamese monarchy's equivalent of the viceroyal office of "uparaja" (อุปราช ; rtgs: "Uparat" ) until the end of the nineteenth century.
 The office-holder was considered second only to the King, and the heir presumptive.
 The office is also referred to in English as "Vice King" and "Second King."
 It originated in the Ayutthaya period and later gained significant powers during the Rattanakosin period.
 Front Palace occupants were usually a son or brother of the reigning monarch.
 The office existed until the death of the last occupant, Prince Vichaichan, in 1885.
 King Chulalongkorn then abolished the office of an heir presumptive, introducing in its stead the Western concept of a crown prince as heir apparent, and styled the new office "Crown Prince of Siam."
The Crown Prince of Thailand (or Siam; Thai: สยามมกุฎราชกุมาร ; rtgs: Sayammakutratchakuman ) is a title held by the heir apparent to the Thai throne.
 First created by King Chulalongkorn (Rama V) in 1886, for his son Prince Maha Vajirunhis, the king's eldest son by a royal wife Queen Savang Vadhana.
 Prior to this, the Siamese throne did not have a law or formal system regulating the royal succession.
 In 1688 King Petracha of Ayutthaya created the title of Front Palace, which by the Rattanakosin period had become the main title granted to the heir presumptive to the throne.
 However few Front Palaces have succeeded to the throne this way, with the exception of King Buddha Loetla Nabhalai (Rama II) in 1809.
 After the Front Palace crisis in 1875, the title of Front Palace was abolished and replaced with the title of Crown Prince, who became heir apparent to the throne.
Sophia of the Palatinate (commonly referred to as Sophia of Hanover; 14 October 1630 – 8 June 1714) was the Electress of Hanover from 1692 to 1698.
 As a granddaughter of James VI and I, she became heir presumptive to the crowns of the Kingdom of England and the Kingdom of Ireland under the Act of Settlement 1701.
 After the Acts of Union 1707, she became heir presumptive to the unified throne of the Kingdom of Great Britain.
 She died less than two months before she would have become queen, and her claim to the throne passed on to her eldest son, George Louis, Elector of Hanover, who ascended as George I on 1 August 1714 (Old Style).
An heir presumptive or heiress presumptive is the person entitled to inherit a throne, peerage, or other hereditary honour, but whose position can be displaced by the birth of an heir apparent, male or female, or of a new heir presumptive with a better claim to the position in question.
 The position is however subject to law and/or conventions that may alter who is entitled to be heir presumptive.
The July Crisis was a diplomatic crisis among the major powers of Europe in the summer of 1914 that led to World War I.
 Immediately after Gavrilo Princip, a Slavic nationalist, assassinated Archduke Franz Ferdinand, heir presumptive to the Austro-Hungarian throne, in Sarajevo, a series of diplomatic manoeuvres led to an ultimatum from Austria-Hungary to the Kingdom of Serbia, and eventually to war.
Cvjetko Popović (Serbian Cyrillic: Цвјетко Поповић; 1896 – 9 June 1980) was a Bosnian Serb who was involved in the 1914 assassination of Archduke Franz Ferdinand of Austria.
The 1910s (pronounced "nineteen-tens", also abbreviated as the "teens") was a decade of the Gregorian calendar that began on January 1, 1910, and ended on December 31, 1919.
 The 1910s represented the culmination of European militarism which had its beginnings during the second half of the 19th century.
 The conservative lifestyles during the first half of the decade, as well as the legacy of military alliances, was forever changed by the assassination, on June 28, 1914, of Archduke Franz Ferdinand, the heir presumptive to the Austro-Hungarian throne.
 The murder triggered a chain of events in which, within 33 days, World War I broke out in Europe on August 1, 1914.
 The conflict dragged on until a truce was declared on November 11, 1918, leading to the controversial, one-sided Treaty of Versailles, which was signed on June 28, 1919.
The Ducal House of Hohenberg is an Austrian noble family that descends from Countess Sophie Chotek (1868–1914), who in 1900 married Archduke Francis Ferdinand of Austria-Este (1863–1914), the heir presumptive to the throne of the Austro-Hungarian Empire.
 As their marriage was a morganatic one, none of their children were in the line of succession to the Austro-Hungarian throne.
 Still, they represent the senior agnatic line of the House of Habsburg-Lorraine.
Maximilian, Duke von Hohenberg ("Maximilian Karl Franz Michael Hubert Anton Ignatius Joseph Maria"; 29 September 1902 – 8 January 1962), was the eldest son of Archduke Franz Ferdinand of Austria-Hungary and his wife Countess Sophie Chotek von Chotkowa und Wognin, Duchess von Hohenberg.
 Because his parents' marriage was morganatic, he was excluded from succession to the Austro-Hungarian throne, to which his father was heir presumptive, and to inheritance of any of his father's dynastic titles, income and properties, although not from the archduke's personal estate nor from his mother's property.
Franz Ferdinand Carl Ludwig Joseph Maria (18 December 1863 – 28 June 1914) was an Archduke of Austria-Este, Austro-Hungarian and Royal Prince of Hungary and of Bohemia and, from 1896 until his death, heir presumptive to the Austro-Hungarian throne.

Question: The person Cvjetko Popović was involved in the assassination of became heir presumptive to the Austro-Hungarian throne in what year?
Answer: 1896