In 1208, Philip of Swabia, the successful candidate to assume the throne of the Holy Roman Empire, was assassinated. As a result, the imperial crown was given to his rival Otto IV, the nephew of King John. Otto, prior to his accession, had promised to help John recover his lost possessions in France, but circumstances prevented him from making good on his promise. By 1212, both John and Otto were engaged in power struggles against Pope Innocent III: John over his refusal to accept the papal nomination for the archbishop of Canterbury, and Otto over his attempt to strip King Frederick II of Germany of the Kingdom of Sicily. Philip decided to take advantage of this situation, first in Germany, where he aided German noble rebellion in support of the young Frederick. John immediately threw England's weight behind Otto, and Philip now saw his chance to launch a successful invasion of England.