the action, fearing that it would leave the Kiev Voivodeship exposed to a pending Russian attack. When von Fürstenberg learned of the plan, he led a force into the archbishopric of Riga and in June 1556 captured the main strongholds of Kokenhusen and Ronneburg. Jasper von Munster fled to Lithuania, but von Brandenburg and Christoph von Mecklenburg were captured and detained at Adsel and Treiden. This resulted in a diplomatic mission to petition for their release being dispatched by the Pomeranian dukes, the Danish King, Emperor Ferdinand I, and the estates of the Holy Roman Empire. A cross-party meeting in Lübeck to resolve the conflict was scheduled for 1 April 1557, but was cancelled due to quarrels between Sigismund and the Danish envoys. Sigismund used the killing of his envoy Lancki by the landmeister's son as an excuse to invade the southern portion of Livonia with an army of around 80,000. He forced the competing parties in Livonia to reconcile at his camp in Pozvol in September 1557. There they signed the Treaty of Pozvol, which created a mutual defensive and offensive alliance, with its primary target Russia, and provoked the Livonian War. 1558–1562: Dissolution of the Livonian Order Russian invasion of Livonia Ivan IV regarded the Livonian Confederation's approach to the Polish–Lithuanian union for protection under the Treaty of Pozvol as casus belli. In 1554 Livonia and Russia had signed a fifteen-year truce in which Livonia agreed not to enter into an alliance with Poland–Lithuania. On 22 January 1558, Ivan reacted with the invasion of Livonia. Many Livonian fortresses surrendered without resistance while Russian troops took Dorpat (Tartu) in May, Narwa (Narva) in July and laid siege to Reval (Tallinn). Reinforced by 1,200 Landsknechts, 100 gunners, and ammunition from Germany, Livonian forces successfully retook Wesenberg (Rakvere) along with a number of other fortresses. Although the Germans raided Russian territory, Dorpat (Tartu), Narva, and many lesser fortresses remained in Russian hands. The initial Russian advance was led by the Khan of Qasim Shahghali, with two other Tatar princes at the head of a force that included Russian boyars, Tatar, and Pomestnoe cavalry, as well as Cossacks, who at that time were mostly armed foot soldiers. Ivan gained further ground in campaigns during the years 1559 and 1560. In January 1559, Russian forces again invaded Livonia. A six-month truce covering May to November was signed between Russia and Livonia while Russia