It is one of the best views on the island: a mile-wide valley framed by wooded headlands stretching away some four-and-a-half miles to the perfect blue of the Pacific. It would be a prime holiday destination if it weren’t for the fact that it is privately owned: the 4,000 acre Kuoloa Ranch on the windward side of the Hawaiian island of Oahu, not far from Honolulu, belongs to the Morgan family and is still a working cattle ranch. Tourists don’t come here.

Which is probably just as well, because anyone looking towards the sea in the late summer of 2000 could have been forgiven for thinking that heaven had been transformed into hell. Explosions, WWII tanks and some 750 soldiers crouched and ran amid the scrub; helicopters hovered overhead; and a small man in a white shirt darted to and fro, directing operations.

If anyone ever earned the title of ‘director’, it is John Woo on Windtalkers, the movie that was being shot on the Kuoloa Ranch during the weeks after Labor Day 2000. What he was directing was a recreation of the pivotal Pacific theatre battle of Saipan (June 1944), which pitted the US Marine Corps against the might of the Japanese Empire. “I was blown away on that first day of filming,” recalls screenwriter John Rice, who was on set. “It was truly amazing to see a thousand men in a valley, tanks rolling by and hundreds of explosions going off in one shot” - there were 280 of them in the one shot, according to producer Terence Chang. “It was such a thrill as a writer to see so many talented people and actors bringing your story to life.”

That day - August 28 - represented the culmination of 10 years of work by Woo and Chang, producers Alison Rosenzweig and Tracie Graham, writers Rice and Joe Batteer and by Hollywood studio MGM to recreate what, for nearly a quarter of a century, remained one of the US military’s most highly classified secrets: the use of Navajo soldiers to provide a code that the Japanese could not break.

Nicolas Cage as Joe Enders, a shell-shocked Marine assigned to protect Navajo code-talkers Ben Yahzee (Adam Beach) and Charlie Whitehorse (Roger Willie).

In an era long before digital encryption technology, communications between headquarters and advanced battle positions, and between battle commanders and the troops on the ground, were extremely vulnerable. As the recent British movie Enigma revealed, cracking the enemy’s code was a priority in every theatre of operations, and especially in the Pacific, where the distances were huge and the possibility of enemy interception even greater.

Previously, the Japanese had successfully ‘hacked’ into almost every US military communications system, endangering both long-term strategic plans and the lives of the soldiers carrying them out. It was Philip Johnston, the son of a missionary, who provided the US Marine Corps with the solution. Johnston had grown up on a Navajo reservation and was one of the few non-Native Americans to speak the incredibly complex language of the Navajo nation. As in Chinese, words in Navajo change their meaning depending on the stress and intonation. Unlike Chinese, however, Navajo has never been written down. And this meant that the chances of the Japanese being able to access its meanings were remote.