Political tensions in England began to rise, however, and a potential conflict between King John and an alliance of rebel barons opposed to his rule began to look likely. In early 1215, King John installed a trusted German mercenary called Ranulph in charge of Berkhamsted Castle and reviewed the defensive arrangements there that April. Civil war broke out later that same year. Initially, the rebels were hampered by a lack of equipment – in particular, siege engines – but in May 1216 the future Louis VIII crossed over the English Channel joining the rebel cause and being proclaimed king in London, bringing with him heavy siege equipment.