after henry's death, the duke of newcastle was prime minister for six years in two separate periods. his first premiership (17541756) was not particularly notable: newcastle partly caused the seven years' war, and his weak diplomacy cost him the premiership. after his second term (17571762), he served briefly in lord rockingham's ministry, before he retired from government. he was most effective as a deputy to a leader of greater ability, such as walpole, his brother, or william pitt the elder.