This allied him to Lithuania and together the two rulers undertook numerous military campaigns against the Kingdom of Poland .
However , in 1255 ( or the previous year ) Shvarn married an unnamed daughter of Mindaugas , since 1253 the first ( and only ) king of Lithuania .
This allied Shvarn to Lithuania and together the two rulers undertook numerous military campaigns against the Kingdom of Poland .
However , in 1255 ( or the previous year ) Shvarn married an unnamed daughter of Mindaugas , since 1253 the first ( and only ) king of Lithuania .