Paul Campion re-mortgaged his house in New Zealand to finance the film. It was originally just going to be made with his money until the New Zealand Film Commission backed the film and provided additional funding.
The German words stamped on the wall of the radio room are a warning: BEI GASGE FAHR ALLE ROTE KNOPFE ANDREHEN, which roughly translates in English to: "In case of gas danger tighten all the red valves".
Joe Tane's character was originally going to be killed off in the opening five minutes when the production was going to be funded by Paul Campion, with only enough money to pay for three actors for the rest of the film.
When Colonel Meyer interrogates Grogan and talks about 'New Zealanders, a bunch of farmers driving around the deserts of North Africa attacking by night and fleeing to hide like cowards' he is referring to the New Zealand section of the Long Range Desert Group, a special forces unit that was originally formed from the New Zealand Army stationed in North Africa.