one of the sons of vladimir i was given the name "boris". as evidenced by the rus' primary chronicle, boris and gleb were sons of vladimir i, born to him by the bulgarian princess. during vladimir's reign in 988 the conversion of the kievan rus' to christianity took place. in this conversion, both ordinary priests and prelates from bulgaria played a significant part. also, with the adoption of the byzantine calendar and the eastern orthodox liturgical calendar, the cult of st. boris entered the rus' orthodox church. in 1015, the princes boris and gleb were killed by their stepbrother sviatopolk i of kiev, who usurped the throne. within a short time, boris and gleb were canonized and ever since, they have been the native soldier-saints most revered among the ukrainians, russians and belarusians.