The word "Krait" which forms part of one of this movie's alternate titles, "Heroes of the Krait", refers to a a wooden hulled fishing boat known as the MV Krait. This vessel was used by Z Special Force in Operation Jaywick to plant bombs on Japanese ships at Singapore Harbour in September 1943 during World War II. The mission successfully sunk seven Japanese ships of war. The boat's original title prior to Allied ownership was "Kofuku Maru". She was renamed the "MV Krait" in 1942 by the Allied Forces when the vessel was handed over to the Australian Military. The boat was named after a Krait which is actually a type of snake. Many Australian Commando Unit vessels have since been named after snakes since the successful Operation Jaywick mission. This movie is based on two WW II Allied missions of which Operation Jaywick is one.
For this film's release in Japan (as "The Southern Cross"), Toho, the Japanese distributor, billed it as their "50th Anniversary Commemoration Film."
The film's opening prologue states: "Z Special Force was a secret operations unit of the Australian Army in World War Two. It was made up of volunteers from all branches of the Allied Forces and came under the direct command of General Douglas Macarthur. Z Special carried out two hundred and eighty four undercover missions in the South West Pacific Area, the most famous being two daring raids codenamed 'Jaywick' and 'Rimau'. In the first of these, the 'KRAIT', a captured Japanese fishing boat set out from Australia on the longest range seaborne raid ever undertaken in the history of war. It penetrated deep into Japanese held territory covering, on the voyage, a total distance of eleven thousand miles. The events depicted in this film are true and are recorded in the military archives of the British, Australian and Japanese forces."
The movie features Z Special Force aka Z Special Unit aka Z Force aka the Services Reconnaissance Department (SRD). This outfit was an Allied Special Foreces WW 2 specialist reconnaissance and sabotage unit which was also the subject of the producers' (John McCallum and Lee Robinson) previous film, Attack Force Z (1981). Z Force went on missions behind Japanese enemy lines in South-East Asia. The unit was comprised mainly of Australians but also included soldiers from New Zealand, Brtitain, Timor and Indonesia.
The actual World War II mission that this movie is based on was Operation Rimau which was undertaken in 1944. This was an Allied mission of Z Special Force and was similar to an earlier mission entitled Operation Jaywick which had been undertaken one year earlier in September 1943. Operation Rimau's aim was to blow-up Japanese ships with limpet mines in Singapore Harbour.