This Africa-set picture concerns about some mercenaries (Rod Taylor, Jim Brown and Peter Carsten) hired by a Congo leader (Calvin Lockhart) to retrieve diamonds from a besieged city by the Simbas . As the movie's MacGuffin is a cache of uncut diamonds valued at US $50 million . They risk their lives facing off nasties and rebel warriors ; confronting several dangers and adventures . Besides , they must help out various inhabitants (Ivette Mimieux , Andre Morrell and others) lay siege and only backed by a boozer doctor (Kenneth Moore). Meanwhile , a locomotive travels through a treacherous countryside in Africa taking on a lot of risks .
The movie is based on real events and dealing with a train-in-peril across hostile landscapes . From start to finish the exciting warlike action is nonstop . In the movie there is tension , suspense , emotion , frenetic action and a little bit of violence when the fights happen ; besides , being fast movement , for that reason results to be entertaining . The movie was made and released about three years after its source novel "Dark of the Sun" by Wilbur Smith had been first published in 1965 . The book was Smith's second novel with this film being the first ever screen adaptation of a Wilbur Smith story and being adapted by screen-writer Ranald MacDougall . Based on historical facts ; thus , creating the independence Republic Congo (1960) with Lumumba , though later there took place a state coup by Mobutu Sese Seko . Tshombe proclaimed the Republic Katanga with the supporting of mercenaries , mine companies and European countries . The civil war bursts and causes destruction , starvation , rampage and millions of deaths . In fact , publicity for this picture declared that it was the first major motion picture to examine the Congo Rebellion which is aka the Congo Crisis aka the Congo Uprising .
Rod Taylor as the tough and two-fisted mercenary is top-notch . However , Clint Walker was the early choice for the lead Captain Bruce Curry role which in the end was cast with Rod Taylor . Ivette Mimieux is enticing and marvelous . This movie re-unites Rod Taylor with Yvette Mimieux eight years after they co-starred in 1960's "The Time Machine" . Furthermore , Jim Brown as the loyal and hunk pal is splendid and agreeable appearance by Kenneth Moore as drunken doctor . Special mention for Peter Carsten who interprets a first-rate villain . Original and thrilling Music by Jacques Loussier , including catching leitmotif . Edward Scaife cinematography is colorful and glittering , as it is splendidly reflected on the awesome jungle outdoors . Picture was lavishly produced by George Englund and well directed by Jack Cardiff , famous cameraman who photographed a lot of classic films . Rating : Above average . Very well worthwhile seeing .