A region across the neck of the Breton peninsula and on the lowest reaches of the Loire in northwestern France, established in the later 8th century, or quite possibly before, to protect Neustria (western Francia) from the Kingdom or Duchy of Brittany. It included Rennes, Vannes and Nantes, and amongst the Marquises was the celebrated Roland who fell at Roncevalles in 778.
Two 9th century Marquises, both called Lambert, who belonged to the powerful Widonid family, which originally came from Burgundy, pursued their own ambitions. The struggles between them and, first, the Emperor Louis the Pious and, later, King Charles the Bald helped to break up the March and to enhance the authority of the Breton leaders.
Louis the Pious used his own Breton appointees as his representatives, and after his death in 840, his Breton ally, Nominoë, was able as King of Brittany to get control of the March. Although the title of lord of the Breton March was still used as late as 921 by Robert, son of the Robert the Strong who had succeeded the executed Lambert II in 852, it referred to his, and his father’s, control of Anjou, the base for the March, rather than the old March.