Philip II’s War with Flanders and the Treaty of Boves (1181–1185 CE)

The city of Amiens, originally known as Samarobriva, was a key strategic settlement in northern France, often contested in medieval conflicts. By the late 12th century, it became central to the war between Philip II of France and Philip of Alsace, Count of Flanders, over the disputed territory of Vermandois, which Philip II claimed as his wife Isabelle of Hainaut’s dowry.

The 1181–1185 War Between Philip II and Philip of Flanders

• In 1181, Philip II launched a campaign against the Count of Flanders, demanding the return of Vermandois, which the Count refused to cede.
• The conflict escalated when the Count of Flanders invaded France, devastating lands between the Somme and the Oise and advancing as far as Dammartin.
• Learning of Philip II’s approach with 2,000 knights, the Count of Flanders retreated toward his own lands, pursued by the French army.
• By 1185, Philip II had successfully broken the Count’s alliances with:
  • Henry I, Duke of Brabant.
  • Philip of Heinsberg, Archbishop of Cologne.
• With his political support eroded and the outcome of a battle uncertain, Philip of Flanders was forced to negotiate peace.

The Treaty of Boves (July 1185)

The Treaty of Boves established a compromise partition of the disputed lands:

• Philip II gained:

  • Amiénois, a key northern region including Amiens.
  • Artois, securing greater Capetian influence in the north.
  • Several other strategic locations.

• Philip of Alsace retained:

  • Most of Vermandois, though it was only granted to him provisionally.

This partial victory strengthened Philip II’s hold over northern France, marking an important step in Capetian expansion.

Philip II’s New Title: “Augustus”

• Following this territorial gain, the monk Rigord began calling Philip II “Augustus”, meaning “the increaser” (augere in Latin means “to augment”).
• The title reflected his success in expanding the royal domain, a trend that would continue throughout his reign.

The Treaty of Boves (1185) set the stage for Philip’s future annexations, reinforcing his role as one of the most ambitious and successful Capetian monarchs.