1st SAS Brigade 1st Special Air Service Brigade ( 1st SAS ) was a fictional brigade during the Second World War . It was first formed in Cairo in 1941 , as part of a deception by Brigadier Dudley Clarke , to play on Italian fears of airborne attacks . Clarke used documents , photographs , news reports and even fake SAS soldiers to plant information about the brigade – he even named the Cairo - based deception department , ' A ' Force , to bolster evidence of their existence . In the summer of 1941 , when David Stirling was pitching his idea for a dedicated airborne commando unit ( which later evolved into the Special Air Service ) he obtained Clarke ' s support partly by promising to use the SAS name . From late 1942 , Clarke used the 1st SAS in his major order of battle deception ( codenamed Operation Cascade ) . The brigade formed part of the fictional 4th Airborne Division ; between then and the end of the war it was used to mislead Axis commanders about the strength of Allied forces in North Africa , and as part of several specific tactical deceptions . Second World War . In late 1940 the Allies recovered the journal of an Italian officer during an operation at Sidi Barrani . The diary referred to fears of British paratroopers being landed to the Italian rear . At the time the Allies had no airborne troops in the North African region . Dudley Clarke , in charge of military deception in the region , decided to play on these fears by creating a fictional airborne unit . Clarke began Operation Abeam in January 1941 by creating a paper trail for the 1st SAS Brigade . The fictional unit was supposedly training for special missions in Transjordan . Clarke established their existence using documentary and physical subterfuge . Photographs of parachutists were printed in local papers , documents were planted with the enemy , Allied airmen were warned to look out for gliders ( Victor Jones mocked up some dummies to support the story ) , and a section of desert was cordoned off for " training " . To aid the rumours , two soldiers were dressed in 1st SAS uniforms and wandered around the Allied - held cities of Cairo , Port Said , and Alexandria , where they were briefed to hint at missions in Crete or Libya . By March , Clarke ' s deception operations had grown and it was decided to create a formal department . He chose the name " Advanced Headquarters ' A ' Force " - the ' A ' being a subtle reference to airborne - in the hope that it would help support the existence of paratroopers in the area ( as well as hide the true purpose of the department ) . Clarke continued actively promoting the existence of 1st SAS until around June 1941 , and it appears that Axis commanders accepted the brigade as real . Clarke had created the unit with no specific aims , although it did mean that the enemy command had to factor the existence of airborne troops into any battle plan . However , Abeam and the 1st SAS represented his first attempt at inflating the apparent strength of Allied forces , a tactic he would use significantly over the rest of the war . The brigade occasionally featured in Clarke ' s tactical deceptions ; such as a March 1941 threat to Axis supply lines near Tripoli . Stirling ' s SAS . In May 1941 , David Stirling , an injured British forces Commando in the North Africa theatre , proposed the idea of small airborne special forces units to operate behind enemy lines . Whilst lobbying for support within Middle East Command it came to Clarke ' s attention , who offered his backing provided the force could also be used to help his own deception schemes . Stirling ' s plan received approval in the summer of 1941 and the unit was designated " L " Detachment , Special Air Service . The name was intended to add further evidence of an airborne presence , specifically 1st SAS , in the region . 4th Airborne . Through 1941 and 1942 , 1st SAS formed part of Clarke ' s overall strategy to deceive the Axis about the strength of Allied forces in the region . In early 1942 , this ad hoc situation was formalised as Operation Cascade ; an entire fictional order of battle featuring numerous units . By late 1942 , the Allies had begun to train a number of real airborne units in the North African theatre . Clarke created the fictional 4th Airborne Division out of several units , both real and fictional , including 1st SAS . Under the umbrella of Cascade , the aim was to mislead the Axis that paratroopers , most of whom were still training , posed a realistic threat . The 4th Airborne were utilised in a number of specific operational deceptions over the next few years ( including Operation Zeppelin and Operation Barclay ) , most often to threaten fictional invasions as a distraction from real Allied operations .