Killer Force, also known as The Diamond Mercenaries, is a 1976 thriller film directed by Val Guest and starring Telly Savalas, Peter Fonda and Christopher Lee.^[1] It was a co-production between the Republic of Ireland, Switzerland, United Kingdom (post production at Twickenham), and the United States and was filmed primarily in South Africa. Its plot is about a gang of criminals who plan a major robbery of a diamond mine.

Val Guest called it "a very tough picture to make."^[2]

Head of security Harry Webb fears that a diamond theft is about to take place at the company's major mining complex in the desert. He quickly manages to become very unpopular, particularly with Claire Chambers, a celebrated cover girl and daughter of the mine administrator. She is visiting the man she loves, Mike Bradley, who is responsible for security at the mine.

Nelson, the mine administrator, gives Bradley a curious mission—to steal a diamond. He wants to implicate Bradley in order to bring him into contact with a certain Lewis who is preparing to rob the mine with the aid of a group of mercenaries and a local accessory known as Father Christmas. Webb, not being informed of the deceit, relentlessly pursues Bradley, who is contacted by Lewis. With the mercenaries in the process of penetrating the mine, Bradley reveals himself to be Father Christmas, the organizer of the entire operation. With Webb in pursuit, Bradley flees into the desert with the only other survivors.

• Telly Savalas ... Webb
• Peter Fonda ... Bradley
• Hugh O'Brian ... Lewis
• Christopher Lee ... Major Chilton
• O. J. Simpson ... Alexander
• Maud Adams ... Clare
• Ian Yule ... Woods
• Michael Mayer ... Adams
• Victor Melleney ... Nelson
• Richard Loring ... Roberts
• Stuart Brown ... Chambers
• Marina Christelis ... Danielle
• Frank Shelley ... Keller
• Peter Van Dissel ... Rick
• Cocky Thlothlalemaje ... Franklyn
• Ian Hamilton ... Doctor
• Dale Cutts ... Plotter
• Don McCorkindale ... Radio Operator
• Marigold Russell ... Salesgirl
• Frank Douglas ... Barman
• Kevin Basel ... Guardhouse Sergeant
• Stuart Parker ... Substation Guard
• Albert Raphael ... Vault Guard
• Russell Newman ... Young Guard
• Clive Scott ... Sky 4 Pilot
• Robert Drayton ... Sky 4 Navigator

The film was based on an original script by Michael Winder which Val Guest says "wasn’t very good in the state it was in and it had an awful lot of changes to be made in it, I took it over and they brought an American writer, Gerald Sanford, and we wrote it between us."^[2]

The film was mostly shot in Swakopmund in Namibia. Guest says they were helicoptered in every morning "into the desert because I wanted to shoot, where people hadn't shot, the dunes were virgin, so … we were dropped in every morning by helicopter, they flew the food in, it was tough going, but again enjoyable."^[2]

Guest says Peter Fonda "was a gentle pain in the arse, Telly [Savalas] couldn't stand him, called him the amateur. “Does the amateur know his lines?” “Yes.” “Well why doesn’t he fucking well say them instead of all these pauses. Fonda would create. He was on the health kick and he’d asked for a blender and it hadn't arrived that morning for his breakfast of three bananas and an almond thing and he refused to come on location till it arrived, and as they’d had to fly in to Windhoek to get it, and fly back, that sort of thing."^[2]

Guest says he was not paid more than $100,000 by the producer, Nat Wachsberger, "another one of filmland’s villains" so the director had to sue. The director says the film "made a fortune of money and Nat just went on a round the world cruise with his wife. Spent it."^[2]