The Kyivan State proper was established by prince Olekh in 879. He conducted military expeditions to the shores of Caspian Sea and raided Byzantine cities.
He was followed, in 912, by prince Ehor, who not only continued external raids but also had to fight insubordinate tribes of Ulitchs and Derevlans. He died during a battle with Derevlans in 945.
His wife Olha revenged his death by brutal suppression of Derevlans. In 964 she became a Christian and established her son Svyatoslav on throne.
Svyatoslav was able and courageous prince; he fought Asian hordes in the East and conducted raids on Bulgaria. He divided his state between his sons, then continued with his expeditions and battles. When he died in 972 during battle with Pechenegs, his sons started to fight between themselves, often with help from their enemies.
In 980, prince Volodymyr defeated all his brothers and unified the country into one powerful state with Kyiv as capital. He adopted Christianity in 988 and started to convert population, who then worshiped Pagan gods, to Christian Religion. Force was often used against those who resisted. He produced silver and gold coins with his portrait on one side and trident on the reverse side ( such special form of trident is Coat of Arms of present day Ukraine). In History he is known as Volodymyr the Great or Saint Volodymyr. During his reign, pillaging Pecheneg hordes defeated Khazars, pushed out Hungarian hordes from southern steppes and became a menace to the state; Volodymyr started to fortify Kyiv against them. After his death in 1015 fighting and assassinations between his sons ensued, resulting in victory for prince Yaroslav in 1019.
Yaroslav the Great consolidated nearly whole of his father's territory, defeated Pechenegs and became one of the most powerful rulers in Europe. A church hierarchy was established, headed (at least since 1037) by the metropolitan of Kyiv, who was usually appointed by the patriarch of Constantinople. Yaroslav promoted family ties with other kingdoms, built many churches, improved Kyiv's fortifications, introduced laws and established courts.
However, same as his forefathers, he divided the country between his sons, who after his death in 1054 started to fight among themselves and divide their land between their sons. This resulted in small principalities who not only fought each other, but also had to defend themselves from marauding Turkish and Polovetsian hordes, who plundered the countryside.
In 1097 all princes agreed to stop fighting between themselves. In 1103 they united their forces under leadership of prince Monomakh (one of the grandsons of Yaroslav the Great) and defeated Polovetsian hordes. However constant warfare weakened country's economic strength and caused near collapse of cultural and political system of Ukraine.
After death of Monomakh in 1125 Ukraine remained fragmented into numerous principalities, having their own customs and rules, with only nominal allegiance to the Prince of Kyiv ( this position was occupied by sons of Monomakh on rotational basis). Gradually Kyiv lost it's power and influence; many principalities separated.
An outstanding chronicle of events was compiled in Old Church Slavonic language by Venerable Nestor in 1136.
In 1169 prince Andrey Bogolyubski conquered and destroyed Kyiv and established his capital in Vladimir near present site of Moscow, thus originating present Russian state.
The Ukrainian princes continued to struggle on against Polovtsi. One particular battle led by Prince Ehor in 1185 was enshrined in a poem "Slovo o Polku Ehorevim" (The Tale of Ehor's Regiment).
Western parts of Ukraine Halych (Galicia) and Volynj (Volhynia) free from Polovetsian raids, gradually emerged as leading principalities. Prince Roman ruled there in 1199. His sons succeeded in uniting both principalities into one rich and powerful state.
About year 1220, when a new horde of Mongols and Tatars invaded Ukraine, the princes have reached some sort of accommodation with Polovtsi and fought together to expel this new horde. They succeeded at first but, toward the end of year 1240, Tatars returned and besieged Kyiv. On 16th December 1240 they conquered, plundered and ruined the city. Afterward they moved westward, plundered Halych, Poland and Hungary then in 1245 they returned and occupied eastern Ukraine.
Meanwhile, Prince Danylo (son of Prince Roman) established himself in Halych and his brother Vasylko in Volynj. Together they managed to keep Tatars away from their principalities. Danylo founded city Lviv in 1250 as a defense site against Tatars. In 1253 he accepted the royal crown from the pope and effected a short-lived church union with Rome.
After Danylo died in 1264, his sons continued to rule in peaceful coexistence with Tatars. In 1303 they created a separate archbishopric office in Halych, responsible to Byzantine, because in 1299 Kyivan archbishopric seat was moved to Moscow.
The dominant prince was Danylo's son Lev; he died about year 1300. His son Yuriy again united Halych and Volynj principalities with Lviv as capital. He was a mighty and just ruler; the country was rich and peaceful under his rule.
After Yuriy, his two sons ruled till about 1320. They both died without leaving male successors. This created unstable situation and internal power struggle, which was exploited by neighboring countries Poland, Hungary and Lithuania in their efforts to occupy this part of Ukraine. Local boyars and People's Councils tried to resist by accepting princes from other dynasties and countries and by forming alliances with Lithuanians and even Tatars, but in 1349, Polish king Kazimyezh managed to occupy Halych and part of Volynj. About same time, Lithuanian princes intensified their takeover of eastern principalities of Ukraine; about year 1360 the Prince of Kyiv was overthrown.
Thus Ukraine was partitioned between Poland and Lithuania with Tatar Golden Horde remaining in some parts of southern steppes and the Crimea.