listen to the lower classes' opinions. And in order to rid himself of the dependence on the starshyna (senior officers), the hetman created the Serdiuk regiments which consisted of 20,000 mercenary infantry units who took orders only from him. When his hetmancy began, Doroshenko, like all Right-bank hetmans, followed a pro-Polish line, but he quickly changed this policy upon hearing the signing of the 1667 Treaty of Andrusovo. The treaty officially divided Ukraine between Russia and Poland, with Russia gaining sovereignty over Left-bank Ukraine and Poland acquiring Right-bank Ukraine. Once the news reached Doroshenko, he reportedly suffered a seizure upon learning of Ukraine's partitioning. Doroshenko quickly deserted his pro-Polish position and decided to seek aid from the Ottoman Empire. War with Poland and Turkish alliance In the fall of 1667 Doroshenko, with support of Crimean Tatars, defeated the Polish forces at the Battle of Brailiv (Brailiv) in Podolia. After the battle, Doroshenko's opposition, led by the Kosh Otaman Ivan Sirko and Tatars stopped his further advance against Poles. With the Right-Bank seemingly secured, Doroshenko and his men crossed into Left-bank Ukraine and supported an uprising of Ivan Briukhovetsky against Russia. Following Briukhovetsky's execution, Doroshenko was proclaimed the hetman of all Ukraine on . As Doroshenko was reaching his zenith of power after successfully reuniting Ukraine, his numerous enemies united against him. The new Polish offensive forced him to return to the Right-bank Ukraine, appointing Demian Mnohohrishny acting hetman of the Left-bank. Doroshenko managed to secure the release from Polish captivity of the Metropolitan of Kiev, Galicia and all Ruthenia — Yosyf Tukalsky-Neliubovych — who moved his seat to Chyhyryn. In January 1668 the Council of Officers (Seniors) in Chyhyryn expressed its support for Doroshenko's intentions to ally with the Ottoman Empire. In autumn of 1668 the Cossack delegation was sent to Constantinople with a proposal for military alliance between the Cossack state and the Ottoman Empire. The alliance was approved again at the 1669 Korsun Cossack Council (General Military Council) on 10–12 March. The alliance was eventually proclaimed by sultan Mehmed IV on 1 May 1669, Doroshenko receiving a title of Sanjak-bey. Separatism of Mnohohrishny, Sukhoviy and Khanenko At the same time in the fall of 1668 Demian Mnohohrishny pledged his allegiance to Russia and on 13 March 1669 his election was confirmed. Also in the fall of 1668 some Zaporizhian Cossacks who opposed Doroshenko elected new hetman the Zaporizhian