The Golden Age of Kievan Rus' began with the reign of Vladimir the Great (980–1015), who turned Rus' toward Byzantine Christianity. During the reign of his son, Yaroslav the Wise (1019–1054), Kievan Rus' reached the zenith of its cultural development and military power.[6] This was followed by the state's increasing fragmentation as the relative importance of regional powers rose again. After a final resurgence under the rule of Vladimir Monomakh (1113–1125) and his son Mstislav (1125–1132), Kievan Rus' finally disintegrated into separate principalities following Mstislav's death.
In the mid-17th century, a Cossack military quasi-state, the Zaporozhian Host, was established by the Dnieper Cossacks and the Ruthenian peasants fleeing Polish serfdom. Poland had little real control of this land (Wild Fields), yet they found the Cossacks to be a useful fighting force against the Turks and Tatars, and at times the two allied in military campaigns. However, the continued enserfment of peasantry by the Polish nobility emphasized by the Commonwealth's fierce exploitation of the workforce, and most importantly, the suppression of the Orthodox Church pushed the allegiances of Cossacks away from Poland. Their aspiration was to have representation in Polish Sejm, recognition of Orthodox traditions and the gradual expansion of the Cossack Registry. These were all vehemently denied by the Polish nobility. The Cossacks eventually turned for protection to Orthodox Russia, a decision which would later lead towards the downfall of the Polish-Lithuanian state, and the preservation of the Orthodox Church and in Ukraine.
With the collapse of the Russian and Austrian empires following World War I and the Russian Revolution of 1917, a Ukrainian national movement for self-determination reemerged. During 1917–20, several separate Ukrainian states briefly emerged: the Ukrainian People's Republic, the Hetmanate, the Directorate and the pro-Bolshevik Ukrainian Soviet Socialist Republic (or Soviet Ukraine) successively established territories in the former Russian Empire; while the West Ukrainian People's Republic emerged briefly in the former Austro-Hungarian territory. In the midst of Civil War, an anarchist movement called the Black Army led by Nestor Makhno also developed in Southern Ukraine. However with Western Ukraine's defeat in the Polish-Ukrainian War followed by the failure of the further Polish offensive that was repelled by the Bolsheviks. According to the Peace of Riga concluded between the Soviets and Poland, western Ukraine was officially incorporated into Poland who in turn recognised the Ukrainian Soviet Socialist Republic in March 1919, that later became a founding member of the Union of Soviet Socialist Republics or the Soviet Union in December, 1922.
On July 16, 1990, the new parliament adopted the Declaration of State Sovereignty of Ukraine. The declaration established the principles of the self-determination of the Ukrainian nation, its democracy, political and economic independence, and the priority of Ukrainian law on the Ukrainian territory over Soviet law. A month earlier, a similar declaration was adopted by the parliament of the Russian SFSR. This started a period of confrontation between the central Soviet, and new republican authorities. In August 1991, a conservative faction among the Communist leaders of the Soviet Union attempted a coup to remove Mikhail Gorbachev and to restore the Communist party's power. After the attempt failed, on August 24, 1991 the Ukrainian parliament adopted the Act of Independence in which the parliament declared Ukraine as an independent democratic state. A referendum and the first presidential elections took place on December 1, 1991. That day, more than 90 percent of the Ukrainian people expressed their support for the Act of Independence, and they elected the chairman of the parliament, Leonid Kravchuk to serve as the first President of the country. At the meeting in Brest, Belarus on December 8, followed by Alma Ata meeting on December 21, the leaders of Belarus, Russia, and Ukraine, formally dissolved the Soviet Union and formed the Commonwealth of Independent States (CIS).
Source: Wikipedia