on 5 april 1356, john ii unexpectedly, and to contemporaries quite shockingly, personally had charles ii arrested while he was attended a council of the leading noblemen of normandy at rouen. and so open war broke out between the houses of evreux and valois as the king of france's armies lay siege to evreux, charles' administrative seat in normandy. it fell to philip to defend his imprisoned brother's interests in normandy. after a brief attempt to negotiate with john ii he withdrew to the cotentin where he set up headquarters at cherbourg and proclaimed himself his brother's lieutenant in france. though the region had a long tradition of opposition to the french crown the local nobility were reluctant to throw in their support as the navarrese caused appeared doomed to fail. philip sent his chief lieutenants martin henriques and pedro remirez back to navarre to raise troops. there louis, the youngest of the three brothers, was already busy raising money and seeking allies in spain and at avignon. however philip knew that the resources of navarre alone could never be enough to sustain a war against france and by the end of april he had sent to emissaries to england to seek an alliance. though initially sceptical by 4 may the english government had decided to divert henry, duke of lancaster's planned invasion of brittany to normandy. on 28 may philip formally renounced his homage to the king of france and declared war on his former liege.