In mid-1100s two major powers on the former Kyiv Empire's territory appear to be Galician Principality, since in 1170s the throne of Galicia was seized by Volhynian Prince Roman Mstyslav, and Volodymir-Suzdal' Principality under the Boholiubsky Dynasty. This period -- between the death of Yaroslav the Wise in 1037 and the first Mongol Aggression in 1248 is not covered very well in the world's history because of Russian and later Soviet shovinism in historiography. But that was the very period, when two dominant Eastern Slavic nations formed -- the Ruthenians (later Ukrainians) and Russians (later Muscovites)-- since nothing could keep different peoples and interests of the Empire together anymore.
Both Great Princedoms -- and that's the way their leaders referred to themselves as -- were more of princely leagues, since they comprised an innumerable number of semi-integrated little princedoms, landowner's ( boyars) estates, nomades and highlander's villages. Both saw the capture of Kyiv as their primary objective for a long time -- the demolishing of Kyiv by Andriy Boholyubsky of Volodymir-Suzdal' and capture of Kyiv by Roman Mstislawitch of Galicia are the most known examples. As Kyiv declined as an economic center, the interests of these new countries turned in different directions.
Galician princes engaged in dynastical marriages or incessant wars with Hungarian, Polish or Vallaccian ( Romanian) nobility and the Galician territory and influence extended all over modern geographic Western Ukraine ( everything to the West from Kyiv), partly Belarus' ( Polozk Princedom), Moldova ( both the one now named the republic of Moldova and the Romanian Moldova to the West from Dnister(Nistru), South-Eastern Poland and Transcarpathia. Galicia under Mstyslawitch Dynasty -- belligerent, glorious and rich state -- became one of the largest European countries and, what the most important -- an ally of Byzantium, and, of course an object of envy to many East European monarchs.
North-East, the Volodymir-Suzdal, had close relations with North European Nations and growing Lithuania and Novgorod Republic, trying not to lose their relationship with Byzantium.
In 1199 The Great Prince Roman of Galicia was killed in a battle with Hungarians. His two sons -- the eldest --Vasyl'ko, and the younger -- Daniel were saved by their relatives from the boyars' anger -- the Boyars, the large landowners, were fed up with the absolute rule of Roman and they started to change princes on the throne fast. When Vasyl'ko became of age, they blinded him. The great internal feud weakened the country.
Daniel, even though becoming of age in the time of trouble, has shown himself as a gifted leader, gathering all forces he could and he suppressed, the boyars oligarchy bloodily and severely in 1220s. Apprehending the Mongol menace after Kalka Battle, in which his predecessor Mstyslav II of Galicia was killed and defeated, Daniel was travelling around Europe seeking for help. The only thing he acquired was a king's crown from the Pope..
Under Daniel, the first king among Eastern Slavic rulers, Galicia was fortified, the new capital was built -- Kholm ( now Khelm in Poland), It ceased back the power it lost after Roman's death and became the strongest among the other Eastern Slavic states.
The first invasion of Eastern Slavic states by Mongols was led by Batu Khan in 1248, who rolled his 400,000 army over Volga River and swept thru South-Eatern princedoms in a matter of two months -- R'yazan'was the first. Batu's straightforward march to Vladimir and Suzdal demolished the North-East princely coalition. Batu's failure to reach Novgorod saved the craddle of the Russian nation from loot and fire but not from vassal dependance on the gigantic Mongolian State, the capital of which, Saray, was set up on the Lower Volga.
Around the same time the 15,000 army of Khan Kuromsah, one of the Batu's chief commanders invaded Kingdom of Galicia, but was defeated and kept back by Galician army led by King Daniel. Mongols could not stand a big independent state on their way to Europe and a 50,000 army of Burunday, the third noble among the Mongols,swept through Galicia and ceased the former capital, Galytch. Daniel was forced to negociate and agreed to become a Mongolian ally, but not to pay tribute. The Galician authority was dramatically reduced comparatively to what it was before, but it still remained, damaged and stripped, an independent country.