Armand Jean du Plessis , better known as Cardinal Richelieu ( 9 September 1585 â `` 4 December 1642 ) was a French clergyman , noble , and statesman . Armand Jean du Plessis de Richelieu , Cardinal-Duc de Richelieu ( ; 9 September 1585 â `` 4 December 1642 ) was a French clergyman , noble , and statesman .