▁to ▁advance ▁in land ▁beyond ▁the ▁protection ▁of ▁the ▁squad ron ' s ▁guns , ▁were ▁effectively ▁imm obil ised ▁at ▁Tour ane . ▁ ▁Capt ure ▁of ▁Sa ig on , ▁ 1 7 ▁February ▁ 1 8 5 9 ▁ ▁Re alis ing ▁that ▁the ▁French ▁g arrison ▁at ▁Tour ane ▁could ▁achieve ▁nothing ▁useful , ▁R ig ault ▁de ▁Gen ou illy ▁decided ▁to ▁strike ▁elsewhere ▁against ▁the ▁Vietnam ese . ▁ ▁He ▁considered ▁and ▁rejected ▁the ▁possibility ▁of ▁an ▁expedition ▁to ▁Ton kin , ▁and ▁in ▁January ▁ 1 8 5 9 ▁proposed ▁to ▁the ▁n avy ▁min istry ▁an ▁expedition ▁against ▁Sa ig on ▁in ▁C och inch ina , ▁a ▁city ▁of ▁considerable ▁strateg ic ▁significance ▁as ▁a ▁source ▁of ▁food ▁for ▁the ▁Vietnam ese ▁army . ▁ ▁The ▁expedition ▁was ▁approved , ▁and ▁on ▁ 2 ▁February , ▁leaving ▁cap itaine ▁de ▁v ais seau ▁Th oy on ▁at ▁Tour ane ▁with ▁a ▁small ▁French ▁g arrison ▁and ▁two ▁gun bo ats , ▁R ig ault ▁de ▁Gen ou illy ▁sa iled ▁south ▁for ▁Sa ig on . ▁ ▁His ▁naval ▁force ▁consisted ▁of ▁the ▁cor v ettes ▁Ph l ég é ton ▁and ▁Prim au gu et , ▁the ▁gun bo ats ▁Al ar me , ▁A val anche ▁and ▁Drag onne , ▁the ▁Spanish ▁des patch ▁vessel ▁El ▁C ano ▁and ▁the ▁trans ports ▁Sa ône , ▁Dur ance ▁and ▁Me ur the . ▁▁ ▁R ig ault ▁de ▁Gen ou illy ▁halt ed