Amicus activity in Croatia at the coastal part of the region Dalmatia, during the period from the fall of
Petar Krešimir IV (d. 1074) to the coronation of
Demetrius Zvonimir (1075), in the scholarship was initially explained as an involvement on the behalf of the Holy See against Petar Krešimir IV due to supposed antagonism among the local clergy towards church reforms. It has been argued that the Croatian king whom Amicus captured was not Petar Krešimir, but rather a certain Slavac, a champion of the Old Church Slavonic liturgy, who had succeeded the childless Krešimir upon the latter's death in late 1073 or early 1074, when his nephew
Stephen was judged unfit and forced to enter a monastery.
Pope Gregory VII allegedly encouraged the expedition of Amicus to remove Slavac and restore the Latin rite. The reign of Slavac is known only from a Renaissance source,
Johannes Lucius, in fact, there was no 11th-century king of that name, but rather a 12th-century nobleman who was mistaken for a king by later generations. At the time, the papal legate to Croatia was
Gerard, who, as the
archbishop of Siponto, was almost a neighbour of Amicus in southern Italy. It was probably his idea to use Amicus to help place Zvonimir, considered an ally of Rome, on the throne. Having been recently deprived of his lordship of Giovinazzo, Amicus was probably easily persuaded to make his fortune in Dalmatia, promised with a land or a principality of his own as a reward. Modern historigraphy rejects such older theorizations, because Petar Krešimir IV was loyal to the Holy See and church reforms. Guiscard, on the other hand, had been excommunicated in 1074 and Amicus would not have felt any need to seek his permission. However, Amicus lost many lands to Guiscard, to get new ones, and possibly found a new Norman-style principality, Amicus was persuaded by the Byzantine emperor
Michael VII Doukas to attack Petar Krešimir IV because the Croatian king abandoned emperor's sovereignty and took in control
Dalmatian cities from the Byzantines, and aided the
Uprising of Georgi Voyteh against Byzantines. Formally, Amicus was invited to Dalmatia by the communes of
Split,
Trogir,
Zadar and
Biograd. He embarked in the spring of 1074, probably from Molfetta, which was in his control, or possibly from
Ancona further up the coast. By 19 March, the Normans occupied several coastal
Dalmatian city-states, including Split, Trogir, Zadar and Biograd. As the next target, according to a late source, Amicus attacked the coast of the
Gulf of Quarnero. Between 14 April and 9 May (
Translation of Saint Nicholas), he besieged the town of
Rab on the
island of the same name. The
Miracula Sancti Christophori of Bishop
Juraj Koštica, written towards 1308, reports that "a large group of Varangians" assaulted Rab. He provides dates, but no year, although from context it appears it can refer only to the expedition of Amicus who, as a Norman, could be described as a "
Varangian" (Viking). In November 1074, Gerard held another synod at Split to reaffirm the decisions of 1060. According to a synodal document, it took place "at the time when duke Amicus took the Croatian king prisoner." Although it does not name the king, Petar Krešimir must be meant. A letter of Pope Gregory VII to Stephen II,
bishop of Zadar, dated to November 1074, also mentions the capture of Petar Krešimir by Amicus. This is the last mention of Krešimir in any source. According to one source, it was while capturing the stronghold of
Novalja on the island of
Pag that Amicus captured the king. While the Croatian king was in captivity, it seems that negotiations between the Papacy, the
ban Zvonimir and the Norman count were ongoing. In a letter to
Sweyn II of Denmark on 25 January 1075, Gregory VII writes that an unnamed Danish bishop had intimated that Sweyn might be willing to send one of his sons with an army to assist the Roman church against its
vulgar and cowardly heretic enemies (Normans) in a land which Gregory does not name but which was almost certainly Croatia. By 8 February 1075, however, Amicus had been substantially defeated through Venetian intervention. He had lost control of the Dalmatian cities of Split, Trogir, Zadar and Biograd, for on that date the Venetian doge,
Domenico Selvo, exacted an oath from four cities that they would never again invite the Normans in. Although Venice had been encouraged by the Byzantines to remove the Normans from Dalmatia (which Krešimir had only governed as a Byzantine province), the Venetian treaty with the Dalmatian cities made no reference to Byzantine authority: "Venice was now a fully autonomous state exercising its sovereignty without reference to any higher authority". The Danish plan by the Pope and Venetian asspirations toward Dalmatia came to nothing as Zvonimir was crowned by Abbot Gebizo with regalia gifted by the pope at
Solin on 9 October 1075 after swearing an oath to the papacy. ==Third rebellion==