Detailed Instructions: In this task, you are given a question and a context passage. You have to answer the question based on the given passage.
Problem:Who was John's rival?, Context: After his coronation, John moved south into France with military forces and adopted a defensive posture along the eastern and southern Normandy borders. Both sides paused for desultory negotiations before the war recommenced; John's position was now stronger, thanks to confirmation that the counts Baldwin IX of Flanders and Renaud of Boulogne had renewed the anti-French alliances they had previously agreed to with Richard. The powerful Anjou nobleman William des Roches was persuaded to switch sides from Arthur to John; suddenly the balance seemed to be tipping away from Philip and Arthur in favour of John. Neither side was keen to continue the conflict, and following a papal truce the two leaders met in January 1200 to negotiate possible terms for peace. From John's perspective, what then followed represented an opportunity to stabilise control over his continental possessions and produce a lasting peace with Philip in Paris. John and Philip negotiated the May 1200 Treaty of Le Goulet; by this treaty, Philip recognised John as the rightful heir to Richard in respect to his French possessions, temporarily abandoning the wider claims of his client, Arthur.[nb 4] John, in turn, abandoned Richard's former policy of containing Philip through alliances with Flanders and Boulogne, and accepted Philip's right as the legitimate feudal overlord of John's lands in France. John's policy earned him the disrespectful title of "John Softsword" from some English chroniclers, who contrasted his behaviour with his more aggressive brother, Richard.
Solution:
Arthur