The first widely known action of the foreign policy of the Ancient Russian state was the establishment of the embassy in Constantinople in 838 - the capital of the Byzantine Empire, the most mighty state of the Eastern Mediterranean Sea and the regions of the Black Sea. The establishment of friendly relations with the Byzantine Empire was the main trend of the Russian foreign policy. War conflicts replaced the periods of lasting peace during which military detachments hired by Russia participated quite often in wars between neighbours on the side of Byzantium. The first Russian campaign to Constantinople took place in 860. Russian troops on 200 boats appeared on the banks of the Bosporus just at the time when Emperor Michael III was at war with the Arabs. The campaign resulted in signing a peace treaty. Soon some of the Ancient Russian nobility were Christianized.
In 907 Kiev and Novgorod prince Oleg (882-912) brought numerous troops to the capital of the Byzantine Empire by sea and by land. The troop included not only the Kiev prince's armed force but also the detachment of the Slavonic unions of tribal principalities and the Varangians - mercenaries dependent on Kiev. As for the hiring of the Varangian detachments, mainly the Sweedish Viking prince's armed forces, it went on during the whole period of the 10th - and the beginning of the 11th centuries. Some mercenaries, who became rich being in service at Kiev prince, returned home, another part of them settled in Russia, joining the Ancient Russian prince's armed force stratum, just as it was in the second half of the 9th century with the members of the Ryurik prince's armed force. The campaign, during which the suburbs of Constantinople were ruined, resulted in signing a peace treaty in 907-911, advantageous for Russia. Their texts, preserved in 'The Story of Temporal Years' - the Ancient Russian chronicle of the 12th century - are the most ancient texts of the Ancient Russian diplomacy and law. According to the treaty of 907, the Russian, arriving in Byzantium to carry on the trade, got a privileged position. The treaty of 911 brought under regulations the Russian-Byzantium relations in the wide range of political and legal problems. Besides, there were some references on 'The Russian Law' - inner legal standards of the Ancient Russian state.
In 941 Prince Igor, the successor of prince Oleg, undertook a new campaign to Constantinople. The breach of the existing treaty on the part of the Byzantines might be the reason of the campaign. Igor's troops sustained a great defeat in a sea battle. Then in the year of 944 the Russian prince together with the Pechenegs made the second attempt. This time the battle was not to be, as a new peace treaty was concluded. The text of the treaty can also be found in chronicles.
Princess Olga entertained friendly relations with the Byzantine Empire. In 946-957 (the date is not precise) she paid a diplomatic visit to Constantinople and was Christianized. But this act did not involve the Russian into mass Christianization.
Foreign policy carried out by Svyatoslav (945-972), Olga and Igor's son, was marked by great activity. But in spite of his mother's persuasions he still remained a heathen. In 964-965 Svyatoslav brought into subjection the Vyatichi, living on the Oka River, reached the Volga, destroyed the Volga Bulgaria (the Muslim state on the Central Volga and the Lower Kama). Then moving down the Volga, he fell upon the Eastern Slavs' enemy - the Khazar kaganate. This once being a mighty state fell under the attacks (the Itil and the Sarkel were conquered). Then the Nomads-Pechenegs completed the defeat. Svyatoslav also brought into subjection the North-Caucasian tribes of the Yas (the Ossets' ancestors) and the Kasog (the Adygeis' ancestors) and it gave start to a new principality on the Taman Peninsula (the Eastern region of the Azov).
In 967 Prince Svyatoslav turned the interests in his foreign policy from the East to the Balkan. Coming into an agreement with the Byzantine Emperor Nikiphor Phoka he took the field against Danube Bulgaria, won the victory and settled the Lower Danube and began threatening the Byzantine Empire. The Byzantine Diplomacy managed to send against Russia the Pechenegs, who took the opportunity of the Russian Prince being away almost took Kiev in 968. Svyatoslav returned to Russia, defeated the Pechenegs and came back to the Danube again. Signing a treaty with Bulgarian Tsar Boris, he unleashed a war with the Byzantine Empire and crossing the Balkan intruded in Phrakia. War actions had a changeable success but in the end Byzantine Emperor John Tsimiskhy assumed the offensive, occupied Preslav, the capital of Bulgaria, and sieged Svyatoslav in Dorostol (on the right bank of the Danube).