The dukes had to face Viking inroads and unrest for over a century, an instability that brought about the destruction of existing monasteries in Gascony and a decayed urban life. The dukes of Gascony faced up against the Norsemen (Vikings), and a king of Navarre is cited as providing assistance against them near Bayonne. The Gascon ducal family became tied to the rising Kingdom of Navarre by matrimonial alliances at the end of the 10th century, eventually bringing Gascony suzerain to King Sancho III of Navarre ("the Great") for a short period up to 1035.