Pope John VIII replied with a letter on June 7, 879, in which he wrote that he celebrated a Mass at the tomb of St. Peter at which he invoked God's blessing on Branimir and his (Croatian) people. In year 925 Croatian King Tomislav was corresponding with Pope John X on the occasion of the first Church Council of Split. The Pope's letter to King Tomislav is the first international document in which a Croatian ruler was called "rex" (king), so that is why Tomislav is considered to be the first Croatian king. On March 13, 1177, Pope Alexander III became the first pope to visit Croatian territories. Pope Alexander visited Palagruža, Vis, Zadar and Rab. He entered Zadar on a white horse, and was welcomed by a huge crowd that was singing songs in the Croatian language. He bowed before the relics of Saint Anastasia. This was documented on the memorial plaque in the Zadar Cathedral. In Rab, the Pope dedicated the Cathedral. This visit, during which he stayed in Zadar for three days, occurred because of a storm that occurred while he was on his way to the Republic of Venice where he signed an agreement with the Holy Roman Emperor Frederick I. During the Croatian–Ottoman Wars that lasted from the 15th to 19th century Croats strongly fought against the Turks which resulted in the fact that the westernmost border of the Ottoman Empire and Europe became entrenched on the soil of the Croatian Kingdom. In 1519, Croatia was called the "Antemurale Christianitatis" by Pope Leo X. After 1527 Croatia was part of the Austrian Empire, which signed a concordat with the Holy See in 1855 regulating the Catholic Church within the empire. In 1918 Croatia become part of the Kingdom of Yugoslavia. Negotiations on the concordat between the Kingdom and the Holy See were led in 1936 by the Yugoslav Minister of Justice Ljudevit Auer and Cardinal Eugenio Pacelli (who later become Pope Pius XII). Negotiations were eventually terminated due to opposition by the Serbian Orthodox Church which claimed that the Catholic Church would be privileged. So the Catholic Church remained the only religious community in the Kingdom which did not have regularized relations with the state. During this period, Stjepan Radić, leader of the Croatian Peasant Party, heavily criticized Catholic clergy, and advocated establishment of the Indigenous Croatian Catholic Church and its separation from the Holy See.