▁issued ▁from ▁the ▁German ▁Foreign ▁Office ▁in ▁January ▁ 1 9 1 7 ▁that ▁proposed ▁a ▁military ▁al liance ▁between ▁Germany ▁and ▁Mexico . ▁If ▁the ▁United ▁States ▁entered ▁World ▁War ▁I ▁against ▁Germany , ▁Mexico ▁would ▁recover ▁Texas , ▁Arizona , ▁and ▁New ▁Mexico . ▁The ▁tele gram ▁was ▁intercept ed ▁and ▁dec oded ▁by ▁British ▁intelligence . ▁ ▁Re vel ation ▁of ▁the ▁contents ▁en rag ed ▁Americans , ▁especially ▁after ▁German ▁Foreign ▁Secretary ▁Arthur ▁Z imm ermann ▁public ly ▁admitted ▁on ▁March ▁ 3 ▁that ▁the ▁tele gram ▁was ▁genu ine , ▁helping ▁to ▁generate ▁support ▁for ▁the ▁United ▁States ' ▁declaration ▁of ▁war ▁on ▁Germany ▁in ▁April . ▁The ▁dec ryption ▁was ▁described ▁as ▁the ▁most ▁significant ▁intelligence ▁triumph ▁for ▁Britain ▁during ▁World ▁War ▁I , ▁and ▁one ▁of ▁the ▁earliest ▁occasions ▁on ▁which ▁a ▁piece ▁of ▁signal ▁intelligence ▁influenced ▁world ▁events . ▁ ▁Tele gram ▁content ▁ ▁The ▁message ▁came ▁in ▁the ▁form ▁of ▁a ▁c oded ▁tele gram ▁dispatch ed ▁by ▁Arthur ▁Z imm ermann , ▁a ▁Staats se kret är ▁( a ▁top - level ▁civil ▁servant ) ▁in ▁the ▁Foreign ▁Office ▁of ▁the ▁German ▁Empire ▁on ▁ 1 9 ▁January ▁ 1 9 1 7 . ▁The ▁message ▁was ▁sent ▁to ▁the ▁German ▁amb assador ▁to ▁Mexico , ▁Heinrich ▁von ▁E ck ard t . ▁Z imm ermann ▁sent ▁the ▁tele gram ▁in ▁anticip ation ▁of ▁the ▁res umption ▁of ▁un rest rict ed ▁sub marine ▁war fare ▁by ▁Germany ▁on ▁ 1 ▁February ,