Military deception
To gain and maintain the element of surprise for Bagration, the Soviets executed a successful deception effort. The overall intent was to make German commanders believe the Soviets would only defend in the center of the front (Belorussia), while launching a major offensive to the south in Ukraine and Crimea and a feint to the north in Finland. Soviet military leaders successfully masked preparations for action in Belorussia and limited German reconnaissance in the center of the front while drawing German attention to deceptive activities in the north and south. Germany was caught off-guard at the start of the Bagration offensive on 23 June, and the Soviets quickly pushed retreating German forces from the Soviet Union all the way to Poland.

Western Front: 

Africa: From early 1941, Dudley Clarke commanded the 'A' Force, based in Cairo, Egypt, which developed much of the war's Allied deception strategy. In an initial deception failure from which Clarke derived an important lesson he put to use in the future, the British intended to retake British Somaliland by an advance from Sudan into Eritrea. Operation Camilla was intended to deceive the Italians occupying British Somaliland into thinking the British intended to retake British Somaliland by an amphibious assault from Aden. Instead of moving their troops to meet the potential amphibious landing, or retreating to Italian-occupied Somalia, the Italians withdrew into Eritrea. As a result, they possessed greater strength at the British objective when the genuine British attack occurred. Clarke's lesson was to focus deception not on what the enemy should think is happening but what the deception planner wants the enemy to do as a result.

North Africa: Deception played an important part in the war in North Africa. In 1941, a British Army unit led by magician and illusionist Jasper Maskelyne prevented the destruction of Alexandria, Egypt by using lights to recreate the nighttime image of the city, while blacking out the actual city lights. Coupled with explosives that simulated German bombs landing on the city, Maskelyne's illusion caused German planes to release their ordnance on the empty coastal site he had prepared rather than on the city.
Maskelyne was subsequently tasked with preventing the Germans from attacking the Suez Canal, a key asset in the Allied supply chain. He responded by creating a system of swirling searchlights which cast a spray of strobe light over more than 100 miles of the sky above Egypt. German pilots were unable to see the canal, and so were unable to destroy it.
As part of the deception surrounding Operation Crusader during the Siege of Tobruk, camouflage artist Steven Sykes built a dummy railhead near Misheifa in Egypt. The intent, which succeeded, was to divert German aerial attacks from the real railhead and deceive the Germans into believing that the British attack would not begin until the dummy was completed. Before the Second Battle of El Alamein, camouflage unit commander Geoffrey Barkas led Operation Sentinel and Operation Bertram, which used dummy equipment and other deceptive measures to deceive German commander Erwin Rommel about Allied strength and the timing and location of the Allied attack.
In Operation Sly Bob, Maskalyne's unit attempted to create a dummy submarine that would draw the attention of German reconnaissance aircraft along the German and Italian Italy-to-Tripoli supply line, enabling British ships to gain the element of surprise when attacking Axis shipping. By using old railroad sleeper cars, a wooden frame, nailed and welded beams, and metal tubing, Maskalyne's unit succeeded in creating a prototype that British ship commanders unaware of the deception plan nearly sank when they observed it near the Suez Canal. The difficulty in creating a viable dummy rendered the project impractical, and Sly Bob was abandoned before it was fully implemented.
Based on the experience with Sly Bob, the British attempted to portray an aging cruiser as a battleship that would pose a threat to German shipping. When the effort proved unsuccessful because the dummy equipment and fixtures added to the cruiser were unrealistic, Maskalyne's team used the partially-dummied cruiser as "sucker bait". With sucker bait, a magician uses an audience's powers of observation against it by allowing members to falsely believe they see through a trick. By appearing to attempt to camouflage the cruiser-turned-dummy battleship, which Maskalyne christened HMS Houdin after magician Jean-Eugène Robert-Houdin, but allowing German observers to see through the camouflage, Maskalyne's team enabled the Germans to conclude on their own that the British were attempting to hide a battleship. Allowing the Germans to believe they had penetrated the camouflage and detected the battleship created in the minds of German military leadership the same risk to German shipping a real battleship would have posed.

Normandy: Before the June 1944 D-Day invasion of Normandy, the Allies launched a deception codenamed Operation Bodyguard. As part of Bodyguard, the Operation Quicksilver deception portrayed First United States Army Group (FUSAG), a skeleton headquarters commanded by Omar Bradley, as an army group commanded by George Patton. In Operation Fortitude South, another component of Bodyguard, the Germans were persuaded that FUSAG would invade France at Pas-de-Calais in the fall of 1944. British and American troops used dummy equipment, false radio traffic and double agents (see Double-Cross System) to deceive German intelligence on the location and timing of the invasion. The Germans awaited the Calais landing for many weeks after the real landings in Normandy, leaving in place near Calais several divisions that could have helped delay or defeat the Normandy attack. By the time the Germans realized the Normandy landings were the actual offensive, Allied units were so well established in Normandy that they could not be dislodged.

Pacific theater: Japan continued diplomatic engagement with the U.S. on several issues of concern throughout late November and into early December 1941 even though attacking ships had sailed from their base in the remote Kuril Islands. The surprise 7 December 1941 attack on Pearl Harbor took place several hours before Japan presented a formal declaration of hostilities and officially broke diplomatic ties. Japan also made extensive use of decoys and other deceptive displays throughout the war, which took on increased importance as the tide of the war went against it in 1944 and 1945.
Prior to the October 1944 Battle off Samar, the Japanese incorporated deception into their plan of attack by luring Admiral William Halsey Jr. into leading his powerful Third Fleet to chase a decoy fleet, a target so inviting Halsey took with him every ship he commanded.
With Halsey's force out of the way, the Japanese intended to attack the Allied landings on Leyte. The U.S. responded with their few remaining forces, the three escort carrier groups of the Seventh Fleet. Escort carriers and destroyer escorts had been built to protect slow convoys from submarine attack, and were later adapted to attack ground targets, but they had few torpedoes, as they normally relied on Halsey's fleet to protect them from armored warships. These ships, organized as Task Unit 77.4.3 ("Taffy 3"), and commanded by Rear Admiral Clifton Sprague, possessed neither the firepower nor the armor to oppose the 23 ships of the Japanese force, which included Yamato's 18-inch guns, but took the initiative and attacked. In addition to ships firing on the Japanese from point-blank range, aircraft including FM-2 Wildcats, F6F Hellcats and TBM Avengers, strafed, bombed, torpedoed, rocketed, and depth-charged the Japanese force until they ran out of ammunition. They then resorted to deception, including numerous "dry runs" at the Japanese ships. Concerned that he faced a larger force than he actually did, Japanese commander Admiral Takeo Kurita decided to withdraw.
During the Battle of Iwo Jima in February and March 1945, Japanese deception included dummy tanks sculpted out of the island's soft volcanic rock. At the Japanese-held airfield in Tianhe District, China, the Japanese painted on the ground the image of a B-29 Bomber that appeared to be on fire. Their intent was for the painted image to appear real to high-flying aircraft, which would lower their altitude to investigate, thus making them targets for Japanese anti-aircraft fire. In addition, the Japanese made extensive use of bamboo-framed dummy aircraft to project airpower and protect their remaining aircraft, straw dummy soldiers and wood weapons that made defensive works appear to be manned, and wood dummy tanks to make infantry soldiers appear to have more combat power than they actually possessed.
The Allies planned an invasion of Japan to take place after the end of fighting in Europe. This plan, codenamed Operation Downfall, had several components, including the Operation Olympic invasion of the southern Japanese island of Kyushu. The deception created to enable Olympic to succeed, Operation Pastel, would have included false attacks against Japanese held-ports in China, as well as Japanese positions on the island of Formosa. The end of the war following the U.S. atomic bomb attacks on Japan ended the need for a ground invasion or a deception plan, so Pastel was never implemented.

At sea: As a liaison to the British Navy early in the war, actor and U.S. Navy officer Douglas Fairbanks Jr. observed and participated in several raiding parties and diversions on the French coast. Upon returning to the United States, Fairbanks proposed to Ernest King, the Chief of Naval Operations the creation of a unit that would plan and execute diversionary and deception missions.