Operation Bertram was a Second World War deception operation practised by the Allied forces in Egypt led by Bernard Montgomery, in the months before the Second Battle of El Alamein in 1942. Bertram was devised by Dudley Clarke to deceive Erwin Rommel about the timing and location of the Allied attack. The operation consisted of physical deceptions using dummies and camouflage, designed and made by the British Middle East Command Camouflage Directorate led by Geoffrey Barkas. These were accompanied by electromagnetic deceptions codenamed Operation Canwell, using false radio traffic. All of these were planned to make the Axis believe that the attack would take place to the south, far from the coast road and railway, about two days later than the real attack.

Bertram consisted of the creation of the appearance of army units where none existed and in concealing armour, artillery and matériel. Dummy tanks and guns were made mainly of local materials including calico and palm-frond hurdles. Real tanks were disguised as trucks, using light "Sunshield" canopies. Field guns and their limbers were also disguised as trucks, their real wheels visible, under a simple box-shaped "Cannibal" canopy to give the shape of a truck. Petrol cans were stacked along the sides of existing revetted trenches, hidden in the shadows. Food was stacked in piles of boxes and draped with camouflage nets to resemble trucks.

Trucks were parked openly in the tank assembly area for some weeks. Real tanks were similarly parked openly, far behind the front. Two nights before the attack, the tanks replaced the trucks, being covered with "Sunshields" before dawn. The tanks were replaced that same night with dummies in their original positions, so the armour remained seemingly two or more days' journey behind the front line. To reinforce the impression that the attack was not ready, a dummy water pipeline was constructed, at an apparent rate of 5 mi (8.0 km) per day. Some days' worth remained to be built at the time of the attack; dummy tanks, guns and supplies were constructed to the south.

After the battle, the captured German Panzerarmee general Wilhelm Ritter von Thoma told Montgomery that he had believed the Allies had at least one more armoured division than they did and that the attack would be in the south. Rommel's stand-in, general Georg Stumme, thought the attack would not begin for several weeks. Bertram had succeeded; when announcing the victory at El Alamein in the House of Commons, Winston Churchill praised the camouflage operation.

Bertram was devised by Dudley Clarke to deceive Erwin Rommel about the timing and location of the expected allied attack by the Eighth Army. It consisted of physical deceptions using dummies and camouflage, concealing real movements, in particular of Montgomery's armour. Bertram was accompanied by electromagnetic deceptions codenamed "Operation Canwell" using false radio traffic. The front line was relatively short: it stretched from the Mediterranean Sea in the north, near El Alamein railway station, to the effectively impassable Qattara Depression in the south, a distance of only about 30 miles (48 km). It was therefore clear to the enemy that the attack must come in this space, and since the only road was in the north, surprise and full-scale attack in any other location might have been thought unlikely. The deceptions were planned to make the enemy believe that the attack would take place to the south, far from the coast road and railway, and about two days later than the real attack.

Soon after his arrival on 8 August 1942, the new Middle East commander, Harold Alexander, visited Geoffrey Barkas's camouflage unit at Helwan to assess its ability to implement Bertram. He looked at everything intently, but seemed most interested in the woodworking shop.

On 16 September 1942, Freddie de Guingand, Montgomery's chief of staff, summoned Barkas and Tony Ayrton to Eighth Army headquarters near Borg-el-Arab. He told them this was to be top secret, that Alexander had been impressed by his visit to Helwan, and that he wanted Camouflage's advice. He introduced Charles Richardson, who worked for Dudley Clarke's secretive 'A' Force and was to implement the deception Montgomery needed. Richardson had not been trained in deception planning, given the accelerated training of staff officers in 1940, nor had he ever prepared a deception plan before. He was determined it should succeed, since, as he wrote, "if it failed it would do far more damage than having no plan at all". De Guingand outlined the basic plan: an attack in the north, along the line of the coast road, with a feint some 20 miles (32 km) to the south. The tanks would take two days to move into battle position from their forming-up positions. Engineering work was already under way. He then astonished them by asking them to hide the hundreds of tanks and field guns, and the thousands of tons of matériel, that were to be used for the decisive attack at El Alamein. Barkas had been hoping for such an opportunity, and now he was being offered the chance to camouflage perhaps the largest desert battle ever attempted.

Barkas and Ayrton went out onto the beach dunes to sit and think. Barkas recalled the sacked Jasper Maskelyne, a stage magician who had briefly worked for him, saying he needed his vanishing tricks now. Ayrton agreed, suggesting they use Sunshields to make the tanks seem to be trucks, and vice versa. By the end of that afternoon they had typed up a plan and presented it to de Guingand and Richardson. They proposed to create two dummy armoured brigades to deploy in the south. They would give the appearance of not being ready by making it seem the tanks had not moved from their forming-up areas (Murrayfield and Melting Pot). Dummy tanks would replace them there; while they would mimic trucks when they arrived in the forward Martello area.