 Complete the following phrase:  Rupert spent the beginning of his teenage years in England between the courts of The Hague and his uncle King Charles I, before being captured and imprisoned in Linz during the middle stages of the Thirty Years War. Rupert had become a soldier early; at the age of 14 he attended the Dutch pas darmes with the Protestant Frederick Henry, Prince of Orange. Later that year he fought alongside him and the Duke of Brunswick at the Anglo-German siege of Rheinberg, and by 1635 he was acting as a military lifeguard to Prince Frederick. Rupert went on to fight against imperial Spain in the successful 