What is "tyrtaeus"

Tyrtaeus (; Tyrtaios) was a Greek lyric poet from Sparta who composed verses around the time of the Second Messenian War, the date of which isn't clearly established, but sometime in the latter part of the seventh century BC. He is known especially for political and military elegies, exhorting Spartans to support the state authorities and to fight bravely against the Messenians, who had temporarily succeeded in wresting their estates from Spartan control.