bo at ▁SM ▁U - 3 9 ▁on ▁ 9 ▁December ▁ 1 9 1 5 ▁in ▁the ▁middle ▁of ▁the ▁Mediter rane an ▁Sea ▁about ▁ 1 4 0 ▁miles ▁sout heast ▁of ▁the ▁island ▁of ▁G av d os . ▁The ▁ship ▁was ▁ha uling ▁ 1 0 , 0 0 0 ▁tons ▁of ▁sod ium ▁nit rate ▁from ▁Anto f ag asta , ▁Chile , ▁to ▁Alexand ria , ▁Egypt ▁when ▁the ▁sub marine ▁was ▁sp otted . ▁The ▁captain ▁of ▁Or ter ic ▁tried ▁ev as ive ▁man eu vers , ▁but ▁the ▁U - bo at ▁was ▁commanded ▁by ▁Captain ▁Walter ▁For st mann , ▁one ▁of ▁the ▁most ▁skill ful ▁and ▁dead liest ▁U - bo at ▁command ers ▁of ▁the ▁war . ▁When ▁it ▁became ▁evident ▁that ▁escape ▁was ▁impossible , ▁a ▁white ▁flag ▁of ▁surrender ▁was ▁ho isted ▁over ▁Or ter ic , ▁but ▁the ▁U - bo at ▁fired ▁tor ped o es ▁anyway , ▁s inking ▁the ▁ship , ▁and ▁killing ▁two ▁Chinese ▁sail ors ▁on ▁board . ▁Captain ▁For st mann ▁subsequently ▁det ained ▁the ▁lif eb o at ▁with ▁the ▁captain ▁of ▁Or ter ic ▁long ▁enough ▁to ▁force ▁the ▁latter ▁to ▁sign ▁a ▁German ▁document , ▁then ▁set ▁him ▁ad rift . ▁A ▁few ▁hours ▁later ▁three ▁lif eb o ats ▁with ▁the ▁surv iv ors ▁of ▁Or ter ic ▁were ▁res cu ed ▁by ▁a ▁British ▁hospital ▁ship . ▁ ▁See ▁also ▁ ▁Portuguese ▁imm igration ▁to ▁Hawai i