. ▁The ▁Germ ans ▁assumed ▁that ▁the ▁cable ▁was ▁secure ▁and ▁used ▁it ▁extens ively . ▁ ▁However , ▁that ▁put ▁German ▁diplom ats ▁in ▁a ▁prec ari ous ▁situation : ▁they ▁re lied ▁on ▁the ▁United ▁States ▁to ▁transmit ▁Z imm ermann ' s ▁note ▁to ▁its ▁final ▁destination , ▁but ▁the ▁message ' s ▁un enc rypted ▁contents ▁would ▁be ▁deeply ▁alarm ing ▁to ▁the ▁Americans . ▁The ▁Germ ans ▁persu aded ▁US ▁Amb assador ▁James ▁W . ▁Ger ard ▁to ▁accept ▁it ▁in ▁c oded ▁form , ▁and ▁it ▁was ▁transm itted ▁on ▁ 1 6 ▁January ▁ 1 9 1 7 . ▁ ▁In ▁Room ▁ 4 0 , ▁N ig el ▁de ▁Grey ▁had ▁partially ▁dec oded ▁the ▁tele gram ▁by ▁the ▁next ▁day . ▁By ▁ 1 9 1 7 , ▁the ▁diplom atic ▁code ▁ 1 3 0 4 0 ▁had ▁been ▁along ▁for ▁many ▁years   and ▁was ▁old . ▁Since ▁Room ▁ 4 0 ▁had ▁had ▁am ple ▁time ▁to ▁re construct ▁it ▁crypt anal yt ically , ▁it ▁was ▁readable ▁to ▁a ▁fair ▁degree . ▁Room ▁ 4 0 ▁had ▁previously ▁obtained ▁German ▁crypt ographic ▁documents , ▁including ▁the ▁diplom atic ▁code ▁ 3 5 1 2 ▁( capt ured ▁in ▁the ▁Mes op ot am ian ▁campaign ), ▁which ▁was ▁a ▁later , ▁updated ▁code , ▁similar ▁to , ▁but ▁not ▁really ▁related ▁to ▁code ▁ 1 3 0 4 0 , ▁and ▁naval ▁code ▁SK M ▁( Sign al buch ▁der