Siege of Château Gaillard

• A major event of the Last War
• Durnin's brother was part of the rangers (Ram's Rogues?) that ended the fight. Source
• Arelor held the line during it.

You know that it refers to a castle in Northern France, which has been held by the English on and off throughout history. While there were a number of battles fought there, if someone refers to "the siege of Château Gaillard" without further context, they are meaning a particular battle, the French besieging an English force about two years before the end of the war. The aggressive siege went for a few months before English reinforcements arrived - it's considered one of the more impressive English victories - both France and England had assumed a fall to French hands prior to seeing just how much tenacity the defenders held.