Date Masamune

was a Japanese daimyo in the Tōhoku region during the Azuchi-Momoyama period and Edo period. He was known as the because he lost the use of an eye. 
Date clan.
In the Edo period, the Date clan were identified as one of the "tozama" or outsider clans, in contrast with the "fudai" or insider "daimyō" clans which were hereditary vassals or allies of the Tokugawa clan.
Date sent troops which fought with the Tokugawa during the Battle of Sekigahara.
Sendai-kō.
The feudal daimyō were sometimes identified with the suffix "-kō" (servant) combined with the name of a place or a castle. 
In 1601, Date built the Sendai castle; and the modern-day city of Sendai developed around it. Sendai"-kō" was one of the ways Date Masamune was described.
Keichō Embassy.
In 1613-1620, Date send Hasekura Tsunenaga on a diplomatic mission to the courts of Philip III of Spain in Madrid and Pope Paul V in Rome.
This historic visit is called the .
Legacy.
In 1991, a minor planet or main-belt asteroid 6859 Datemasamune was named after this Edo period historical figure.