Swedish – Novgorodian Wars Swedish – Novgorodian Wars were a series of conflicts in the 12th and 13th centuries between the Republic of Novgorod and medieval Sweden over control of the Gulf of Finland , an area vital to the Hanseatic League and part of the Varangian - Byzantine trade route . The Swedish attacks against Orthodox Russians had religious overtones , but before the 14th century there is no knowledge of official Crusade bulls issued by the Pope . Background . Scandinavians enjoyed trade - and other relations with Novgorod from the Viking Age s onwards . Merchants from Gotland had their own trading house , Gutagård , and the St . Olof church in Novgorod . There were also isolated Scandinavian raids on Novgorod . Eiríkr Hákonarson raided Ladoga in 997 , followed by his brother Sveinn Hákonarson in 1015 . After Yaroslav I ' s marriage to Ingegerd of Sweden in 1019 , Ladoga was made a jarldom in the orbit of Kievan Rus . It was ruled by Ragnvald Ulfsson , father of King Stenkil . There were dynastic marriages between Russian and Scandiniavian royal families e . g . Stenkil ' s granddaughter Christina married Mstislav of Novgorod , upon whose death in 1132 Novgorod seceded from Kievan Rus . The major turning point into more permanent conflict between Sweden and Novgorod arrived with Sweden ' s firmer organization into the Catholic Church in the 12th century and papal requests for crusades against lands controlled by the Orthodox church . Fighting resumes . The 12th century is poorly documented in Sweden , and Russian documents are fragmented . From the surviving sources , however , it seems evident that the newly founded republic and Sweden drifted into hostilities that could not be permanently settled ever again . According to the First Novgorod Chronicle , the Swedish troops attacked the Novgorod merchants somewhere in the Baltic Sea region and killed 150 Novgorodians in 1142 . It is the first known case of hostilities between Sweden and Novgorod . In 1164 , a strong Swedish fleet approached Ladoga but was soundly defeated with most of its ships captured by Novgorod . It is also claimed that Novgorodians and their Karelian allies launched pirate raids against mainland Sweden during the 12th century . During one of such raid , as a legend has it , they brought to Novgorod the doors of the Sigtuna cathedral as a prize . However , there is no certainty on the background of the destroyers of Sigtuna . Swedish sources call them just " heathens " and Novgorodian sources say no word about the event , which would be least expected had they conducted it . Swedish sources also claim that Jon jarl spent nine years fighting against Novgorodians and Ingrians at the end of the 12th century . These expeditions are not documented in Russian sources . Battle of the Neva . After a long pause in open hostilities , Swedes undertook an attack against Novgorod in 1240 . Only source of information on the attack is the First Primary Chronicle written 100 years after the attack . The attack has been speculated to have been led by Birger Magnusson , who was elevated to the position of jarl in 1248 . The only enemy leader named by the chronicle was " Spiridon " who was killed in the battle . Attempts to identify Spiridon with Birger have been made Soon after their fleet entered the mouth of the Neva River , the Swedes were roundly defeated in the famous Battle of the Neva by a young prince , Alexander of Novgorod , who would later be given the epithet " Nevsky " to memorialize this victory . From then on , Sweden moved its interest to Finland . Its troops did not return to Neva before the end of the 13th century , when it had gained solid control of Finland . Earlier , Swedes had also tried to establish a bridgehead in Estonia , in vain . Focus moves to Finland . Apart from Ladoga , Novgorodian interests clashed with Sweden ' s in Finland , a country which Russian forces sacked on numerous occasions from the 11th century onward . The raid in winter 1226 - 1227 led to heavy losses on the Finnish side . A Finnish retaliatory raid against Ladoga in 1228 ended in disaster , contributing to the Finns ' subjugation by the Catholic Swedes during the Second Swedish Crusade in 1249 . Seven years later , the Novgorodians devastated Swedish Finland again . In 1293 the Swedes won a part of western Karelia and built the fortress of Viborg ( Russian : Vyborg ) there . This expedition has traditionally been dubbed as the Third Swedish Crusade . Seven years later , they founded the fortress of Landskrona in the mouth of Neva , on the river Okhta , and ruined the Novgorod settlements on the Neva . Later that year , the Novgorod troops retaliated by destroying Landskrona . In the early 14th century , military tensions escalated and the two powers were continually at war . In 1311 , the Novgorodians devastated central Finland , where the Swedes had recently built a new castle . In response , a Swedish fleet embarked towards Ladoga and set that trade emporium on fire . Three years later , the Karelians ' discontent with Novgorod ' s rule broke out into the open , as they killed Russian governors and sought for help in Sweden . After several months of hostilities , Karelia submitted to Novgorod ' s authority again . In 1318 , Novgorod attacked Åbo ( Finnish / contemporary English : Turku ) in southwestern Finland , burning the city and the cathedral as well as the episcopal castle in Kustö ( Finnish : Kuusisto ) . Four years later , they besieged Viborg and founded Oreshek , an important fortress dominating the entrance to Lake Ladoga . Treaty of Nöteborg and its aftermath . The first treaty concluded by the parties to the conflict was the Treaty of Nöteborg ( August 12 , 1323 ) , followed by the Treaty of Novgorod between Novgorod and Norway in 1326 . The treaties were expected to bring " eternal peace " to the region , but turned out to provide only a temporary palliative . As early as 1328 , Sweden was encouraging settlers to take over the northern coast of the Gulf of Bothnia , which was defined by the treaty as Novgorod ' s possession . When Karelians rebelled against Novgorod in 1337 , King Magnus Eriksson sent his troops in their support , managing to briefly occupy Korela Fortress . Next year , Novgorod besieged Viborg but an armistice was soon agreed upon . After ten years of peace , the king felt ready to renew hostilities and demanded the Novgorodians to recognise the Pope ' s authority . According to the Novgorodian First and Fourth Chronicles , the king demanded that the Novgorodians debate with his " philosophers " ( Catholic theologians ) and whoever lost would become the religion of the winner . Novgorodian Archbishop Vasily Kalika conferred with the " posadnik " and other members of the city ' s elite and told the king that , since they had received Christianity from Constantinople , he should send his philosophers there to debate with the Byzantines . Having received such a response , the king sent his army to Oreshek and set it ablaze . Novgorod soon recovered the lost ground . The king attempted yet another fruitless attack in 1350 . In the same year , the Black Death broke out in Northern Europe , effectively ending further hostilities . Later developments . Later skirmishes were more sporadic . Sweden ' s attempts to control the Gulf of Bothnia provoked Novgorod to start construction of a castle near the Oulu River delta in the 1370s . Sweden replied by establishing their own castle nearby . Novgorod assaulted it in 1377 , but was unable to take it . In the following year , Pope Gregory XI intervened and issued a crusade bull against Novgorod . Soon afterwards the Russians retreated from Ostrobothnia , leaving it for the Swedes . In the late 14th century , the Novgorodians set up the fiefs of Korela , Oreshek , Koporye , Luga , and Ladoga as a sort of buffer state between their core dominions and Sweden . Several Lithuanian dukes renowned for their military skills were invited to rule this Ingrian duchy : Narimantas , his son Patrikas , and then Lengvenis . They helped fortify the Russian - Swedish border and built several new forts in the region , including one in Yama . Hostilities between the two powers were renewed in 1392 and 1411 . However , Sweden had , by then , become a member state in the quarrelsome Union of Kalmar , and was preoccupied by the Scandinavian power struggle for the entire 15th century . The last conflict took place in 1445 , several decades before Novgorod was absorbed into Muscovy . Novgorod ' s demise did not result in peace , however , and conflict continued between Russia and Sweden until the early 19th century .