Singapore. Attack On: Period of Warning Of: Memo. By War Office

5. It therefore appears that warning can only be obtained by visual observation of the convoy. In the case of an expedition from Japan, this might be given by H.M. Ships or aircraft operating from Hong Kong; the some would not necessarily apply in the case of an expedition starting from HAINAN or KAMRANH bay, which would probably first come under observation by ships or aircraft operating from Singapore. As KAMRANH Bay is barely 3 day's steaming from Singapore this should be taken as the minimum period of warning that can be relied upon.