It began in July 1355 and aimed to recover the patrimonial estates of the House of Évreux, which were threatened by the King of France. The expedition, composed of 2,000 Navarrese, departed from Fuenterrabía, stopping in Bayonne, then an English-held city.
From 1356 to 1357, the Navarrese king, an important player on the European chessboard (Hundred Years’ War), was held prisoner at Arleux and, after his release, became the master of the situation. But upon the death of Étienne Marcel, his star waned.
Although new ships left our port under the command of Muñoz de Salt with 334 Navarrese and Guipuzcoans, Charles II concluded peace in October 1360. Guipuzcoan support stemmed from the rapprochement policy initiated by the King of Évreux from the very start of his reign, a policy that crystallized in the pacification of the muga (border) Navarre and Guipúzcoa and in the vassalage sworn by various Guipuzcoan lords, such as the Oñaz, Blastegui, Lazcano, etc., to the Navarrese king.
Once peace was broken, he again used the Guipuzcoan ports to send troops to Cherbourg in 1356.