Boleslaw I ' s intervention in the Kievan succession crisis , 1018 The intervention in the Kievan succession crisis of 1015 – 1019 by the Polish ruler Bolesław Chrobry was an episode in the struggle between Sviatopolk I Vladimirovich ( " the Accursed " ) and his brother Yaroslav ( " the Wise " ) for the rulership of Kiev and Kievan Rus ' . It occurred when Sviatopolk ' s father - in - law Bolesław , ruler of Poland , intervened on Sviatopolk ' s behalf . The intervention was initially successful as Bolesław defeated Yaroslav ' s armies , and temporarily secured the throne for Sviatopolk . But when Bolesław withdrew himself and his army from Kiev , Sviatopolk was unable to retain his position , being defeated by Yaroslav in the following year . Chronicles of the expedition include legendary accounts as well as factual history and have been subject to varied interpretations . Background . The ruler of Poland , Bolesław I , and the ruler of Kiev , Vladimir I , had previously fought over the Cherven towns ( in what was later called Red Ruthenia ) in a conflict that ended favorably for Vladimir . Furthermore , Bolesław , who already had two wives , wanted to marry Predslava , one of Vladimir ' s daughters , in order to cement ties between the two families . Despite Bolesław ' s best efforts , the offer was refused and instead he had to accept a less prestigious connection to the house of Vladimir through the marriage of Bolesław ' s daughter to Vladimir ' s son , Sviatopolk . Between 1005 and 1013 , Vladimir arranged Sviatopolk ' s marriage to Bolesław ' s daughter , whose name has not survived in sources . It is possible that Vladimir decided that neither Sviatopolk nor Yaroslav would succeed to the Kievan throne after his death , as both Sviatopolk and Yaroslav revolted against their father . Vladimir perhaps intended that Sviatopolk would only receive the remote town of Turov ( " Turaŭ " ) after his death , and perhaps choosing his younger sons , Boris and Gleb , as successors despite Sviatopolk being older . Although Sviatopolk is known to have been older than Boris and Gleb , the exact birth order of Vladimir ' s sons is not known and Sviatopolk is alleged in some sources to have been a bastard . Perhaps unhappy by his rule being restricted to only a small appanage , Sviatopolk plotted to overthrow his father . Those theories , however , are based on very little evidence , and in the words of two historians , the origins of their " quarrels with their father are obscure " . According to Thietmar of Merseburg , Bolesław encouraged Sviatopolk ' s revolt through his daughter and the latter ' s wife , though he does not specify the goal of the revolt . Sviatopolk ' s conspiracy was , in the event , thwarted by Vladimir , who called Sviatopolk and his entourage to Kiev and jailed them in 1013 . The planned overthrow , if it existed , may have been supported by Bishop Reinbern of Kołobrzeg , who had traveled with Bolesław ' s daughter . According to the same chronicler , Reinbern actively took part in converting pagans in and around the Rus lands , but was imprisoned with Sviatopolk and the latter ' s wife . Reinbern , who might have acted in the interest of Catholic Rome , died shortly after being imprisoned . It is of note that Bolesław invaded Kiev ' s lands in 1013 . This was possibly Bolesław ' s first attempt to re - take the Cherven towns , though it has also been argued that his goal might have been to free Sviatopolk . Death of Vladimir . Just before Vladimir died , he had sent his son Boris on campaign against the nomads in the south . According to the " Primary Chronicle " , Sviatopolk seized Kiev while those of Vladimir ' s retainers who were with Boris on campaign encouraged Boris to take power , an offer Boris refused apparently stating " Be it not for me to raise my hand against my elder brother " . In the confusion resulting from the death of Vladimir Sviatopolk was able to seize power in Kiev , as Yaroslav was in the north , Mstislav in the south , Sviatoslav in the Derevlian land , Gleb in Murom and Boris on the aforementioned expedition against the Pechenegs . As Franklin and Shepard put it , Sviatopolk ' s " previous arrest turned to his advantage , for it ensured that he was already . . . closest to the center of power " . According to the " Primary Chronicle " , Sviatopolk successfully arranged the murder of three of his brothers , Boris of Rostov , Gleb of Murom and Sviatoslav of the Derevlian lands . When news of the fratricide s reached Vladimir ' s fourth son , Yaroslav the Wise in Novgorod , he came to Kiev from the north with Novgorodians and Varangians . Sviatopolk ' s reign in Kiev was threatened . After a 3 month stand - off near Lyubech , Sviatopolk was defeated and " fled to the Poles " . Bolesław , who had recently agreed a peace with the German Kingdom ( the Treaty of Bautzen ) , agreed to support his son - in - law through military intervention . Sources . There are three main sources that provide historians with evidence for these events . The best and most reliable account is from a chronicle by Bishop Thietmar of Merseburg , who obtained detailed information from Saxon knights fighting for Bolesław . The " Primary Chronicle " attributed to Nestor the Chronicler is another sources giving a detailed account of events , its reliability being variable , depending event - by - event on the sources from which it was compiled . Nestor ' s writing reflects the typical Rus ' admiration of Saint Vladimir , while Bishop Thietmar ' s account , despite a generally positive attitude towards the Rus ' , paints both Bolesław and Vladimir exclusively in a negative light . A third source is the " Chronicle of Polish Dukes " , a semi - legendary ode to the early Polish dukes written in the 1110s by the Benedictine monk Gallus ' . This account portrays Bolesław in a very positive light . Expedition to Kiev . According to Thietmar , the army of Bolesław crossed the border in 1018 and reached Kiev later that same year . Little is known about the armies . Thietmar relates : " Among those rendering assistance to the aforesaid duke , were three hundred of our [ German ] warriors , five hundred Hungarians , and one thousand Pechenegs " . Polish historian Rafał Jaworski states that the estimates of the size of Bolesław ' s army range between 2 , 000 – 5 , 000 Polish warriors , in addition to Thietmar ' s reported 1 , 000 Pechenegs , 300 German knight s , and 500 Hungarian mercenaries . Less is known about Yaroslav ' s army , but it is assumed that he managed to collect a force of similar size . It is also believed that he was aware of Bolesław ' s intentions and had time to make defensive preparations . The narrative of Bolesław ' s invasion is almost entirely dependent upon the account of Thietmar : " We may not keep silent regarding the sad and harmful events that occurred in Russia . For , on our [ German ] advice , Boleslav attacked it with a large army and caused much destruction . On July 22 , the duke [ Boleslav ] came up to a certain river , where he ordered his army to set up camp and separate the necessary bridges . Also camped near the river , along with his army , was [ Yaroslav ] the king of the Russians . " Probably after concentrating his forces during June , in July Bolesław led his troops to the border - the banks of the Southern Bug River , near one of the settlements of the Volhynia region . In the meantime , Bolesław ' s Pecheneg allies approached Kiev , forcing Yaroslav to detach a part of his forces to ensure the safety of his capital . According to Jaworski , Yaroslav , in turn , wanted to prevent Bolesław from uniting with the Pechenegs , defeat Bolesław ' s main force and then take care of the less organized Pechenegs . The two armies met on opposite banks of the River Bug . Yaroslav ' s forces may have take position with archers covering the crossing points . Bolesław seems to have taken his time , allowing his army to rest , and started work on makeshift bridges . The Battle of the River Bug finally occurred around July 23 . Thietmar ' s near - contemporary account offered the following : The Poles provoked the enemy into fighting and , with unexpected success , drove them from the river bank which they [ the Rus ] were supposed to defend . Elated by this news , Boleslav hastily notified his companions and quickly cross the river although not without effort . In contrast , the hostile army , drawn up in battle formation , vainly attempted to defend its homeland . It collapsed at the first attack , however , and failed to mount any effective resistance . Among those who fled , many were killed , but only a few of the victors were lost . On our side , the dead included Erich , an illustrious knight whom our emperor had long held in chains . From that day on , with every success , Boleslav drove the scattered enemies before him ; and the whole populace received and honoured him with many gifts . According to the later " Chronicle of Polish Dukes " by Gallus , the battle occurred by accident : When Bolesław decided to throw a feast to boost his army ' s morale , Yaroslav ' s archers and scouts decided to create trouble for the Polish servants who were gutting the animals and preparing them near the river . However , they only annoyed them enough that the servants themselves crossed the relatively shallow river and chased away Yaroslav ' s surprised troops , who had been guarding the river . Bolesław learned of the skirmish sooner than Yaroslav , and managed to move most of his army across the river , defeating the surprised Yaroslav . The Russian " Primary Chronicle " gives a different version of events , in which both armies were combat ready and separated by the river before Bolesław , enraged by insults from across the river , charged with his army , surprising Yaroslav and scattering his forces . All accounts agree that the Polish prince was victorious in the battle . Yaroslav retreated north to Novgorod , rather than to Kiev - likely suspecting that he lacked enough strength to defend Kiev , which was besieged by the Pechenegs and had a significant pro - Sviatopolk faction within its walls . Nestor notes that after reaching Novgorod , Yaroslav attempted to flee " overseas " in hopes of coming back with a Varangian force , but according to the " Primary Chronicle " , the citizens of Novgorod pressured him to lead the fight back to Bolesław and Sviatopolk . Fall and occupation of Kiev . Bolesław ' s victory opened the road to Kiev , already under harassment from his Pecheneg allies . At Boleslav ' s instigation , the very strong city of Kiev was disturbed by the constant attacks of hostile Pechenegs and severely weakened by fire . It was defended by the inhabitants , but quickly surrendered to the foreign warriors , after its king [ Yaroslav ] fled and abandoned it . The city , which suffered from fires caused by the Pecheneg siege , surrendered upon seeing the main Polish army on August 14 . The entering forces , led by Bolesław , were ceremonially welcomed by the local archbishop and Vladimir ' s family : On 14 August , the city received Boleslav and Sventipolk [ i . e . Sviatopolk ] , its long - absent lord . Thereafter , through his favour , and from fear of us , the whole region was brought into submission . When they arrived , the archbishop of that city received them , at the church of St Sophia , with relics of the saints and other kinds of ceremonial apparatus . A later popular Polish legend related to the history of the Polish coronation weapon , the Szczerbiec sword , is the tale of the Golden Gate of Kiev , upon which the Szczerbiec was supposedly notched when Bolesław ' s entered the city . This legend has no historical basis , however , and the gate was only built approximately 20 years later , while the sword itself was not forged until 200 years later . It is of course possible , however unlikely , that Bolesław notched another gate with another sword , thus giving rise to the legend . Bolesław sent his German and Hungarian mercenaries home after Sviatopolk was re - established on the Kievan throne , " the populace " having " flocked to him " and having " appeared loyal " . It is not known how long Bolesław remained in and around Kiev . The 10 months given by the unreliable account of Gallus is fanciful . Bolesław in fact departed within a few months and , as Thietmar died on December 1 , 1018 , Bolesław must have been back in Poland a good time before December . The " Primary Chronicle " alleges that as the result of Polish plunderings , Sviatopolk ordered " that any Lyakhs [ i . e . Poles ] found in the city should be killed " . The resulting unrest , according to the same source , forced Bolesław to leave Kiev , whereupon Sviatopolk was left to fend for himself . This negative turn of events is omitted in the only contemporary source , Thietmar of Merseberg ' s " Chronikon " . By contrast , his summary of the expedition , written in a part of the " Chronikon " not devoted to the expedition , recounts that : Duke Boleslav invaded the Russian king ' s realm with his army . After placing his long - exiled brother - in - law , the Russian ' s brother , on the throne , he returned in high spirits . According to Thietmar , Bolesław asked Yaroslav to return his daughter , whom Yaroslav had taken prisoner . As Yaroslav refused , Bolesław took members of Yaroslav ' s family to Poland as prisoners when he returned to his country in September . His captives included Vladimir ' s widow and Yaroslav ' s sister , Predslava , whose hand Bolesław had sought earlier . Having been rebuffed , Bolesław now took her as a concubine . The Polish duke also took some commoners as well as much of the treasury of Kiev . Among the notable commoners was the venerated Saint Moses the Hungarian . In the past some historians ( such as Zhylenko and Kostomarov ) have conjectured that Bolesław decided to rule Kievan lands himself , though Bolesław had no power base there and no Rurikid blood . Bolesław ' s main motivation , according to the interpretations of modern historians , was to regain the Cherven towns for his patrimony , while at the same time aiding his kinsman , to whom he had an obligation . The expedition also furnished an occasion to enrich his followers from Kiev ' s famous wealth . Bolesław , soon after his arrival , sent a significant force to quarter in Kiev and nearby towns , forcing Kievans to sustain them , and collected significant tributes that he divided among his allies . It was related by Thietmar that before departing , Bolesław was shown an unspeakable amount of treasure , most of which he distributed among his friends and supporters . On many later occasions in the Kievan period the rulers of Poland , as well as Hungarians or Pechenegs , were paid to intervene in Rus succession disputes ; in the case of Bolesław II , the Polish monarch took the money without making any expedition . Aftermath . Sviatopolk lost the throne soon afterwards and lost his life the following year . As Bolesław was involved in a conflict with Holy Roman Emperor Henry II , he did not intervene on behalf of his son - in - law when he was deposed and instead signed a pact with Yaroslav , who had successfully regained the throne . Although he lost control of Kiev , Bolesław succeeded in keeping the Cherven Towns captured by Vladimir the Great in 981 ; he was crowned King of Poland in 1025 . Yaroslav outlived Bolesław and contributed greatly to the strengthening of Kievan Rus ' . Notes . a The estimate is based on the work of Polish historian Rafał Jaworski .