During the truce of 1206–1208, John focused on building up his financial and military resources in preparation for another attempt to recapture Normandy. John used some of this money to pay for new alliances on Philip's eastern frontiers, where the growth in Capetian power was beginning to concern France's neighbours. By 1212 John had successfully concluded alliances with his nephew Otto IV, a contender for the crown of Holy Roman Emperor in Germany, as well as with the counts Renaud of Boulogne and Ferdinand of Flanders. The invasion plans for 1212 were postponed because of fresh English baronial unrest about service in Poitou. Philip seized the initiative in 1213, sending his elder son, Louis, to invade Flanders with the intention of next launching an invasion of England. John was forced to postpone his own invasion plans to counter this threat. He launched his new fleet to attack the French at the harbour of Damme. The attack was a success, destroying Philip's vessels and any chances of an invasion of England that year. John hoped to exploit this advantage by invading himself late in 1213, but baronial discontent again delayed his invasion plans until early 1214, in what would prove to be his final Continental campaign.