 When he was elected king , the Great Powers extracted a pledge from Otto 's father to restrain him from hostile actions against the Ottoman Empire . Also they insisted that his title be " King of Greece " instead of " King of the Hellenes " , because the latter would imply a claim over the millions of Greeks then still under Turkish rule . Aged not quite 18 , the young prince arrived in Greece with 3 @,@ 500 Bavarian troops and three Bavarian advisors aboard the British frigate HMS Madagascar . Although he did not speak Greek , he immediately endeared himself to his adopted country by adopting the Greek national costume and <unk> his name to " Othon " ( some English sources , such as Encyclopaedia Britannica , call him " Otho " ) . 
