[3] The film's story is inspired by the exploits of units such as the Long Range Desert Group, Popski's Private Army and the SAS in North Africa during the Second World War.

Douglas is then introduced to Cyril Leech, a convicted criminal rescued from prison to lead Masters' operations in the field.

The next day, Douglas and Leech are provided with armed jeeps and lead six other men out into the desert disguised as an Italian Army patrol: the Tunisian Sadok (demolition man), the Greek smuggler Kostas Manou (armorer), Boudesh (communications), the Cypriot Kafkarides (transport and supplies), and the arab guides Hassan and Assin.

They endure a long and arduous trek across the desert: encountering hostile tribesmen, sandstorms and a booby-trapped oasis, among other dangers.

Having lost contact with the men for some time, Masters is ordered to leak intelligence on the team to the Germans; the British Army is now on the offensive, and it wishes to keep any enemy fuel depots intact for capture.

Under the cover of night, the men don German uniforms and sneak into the port depot to plant their explosives, but one of them sets off a trip flare and they are quickly surrounded; an officer on a loudspeaker calls each of them out by name, revealing Masters' betrayal.

Back in the ambulance, while waiting for the rest of the men to return, the injured team member, on his deathbed, uses his last strength to murder the German nurse bound and gagged beside him.

The film was originally titled Written in the Sand;[4] it was announced in October 1967 with Michael Caine to star and René Clément to direct.

[7] In February 1968 Richard Harris and Nigel Davenport signed to co-star, by which time the film had been re-named Play Dirty.

[15][16] De Toth later said that in making the film, "I wanted to rub our noses in the mess we have created and how we shy away from our ability to clean it up...