sentences:  Mingrelia was established as an independent Principality in 1557 with Levan I Dadiani serving as a hereditary "mtavari" (Prince).It remained independent until it became a subject to Imperial Russia in 1803.This came after it signed a patronage treaty with the Russian Empire, which was concluded in return for Russian protection against the harassment of Mingrelia's more powerful neighbors, Imeretia and Abkhazia.