Military deception
Seeing the Gauls appear to retreat, the Romans would advance into the bowl shape or sack created by the bending of Hannibal's line. Once inside the sack, the African infantry positioned on the left and right would wheel inwards and attack the Roman flanks. In combination with the Carthaginian cavalry, the infantry on the flanks would continue moving until they encircled the Romans and could attack their rear. The battle unfolded as Hannibal had envisioned. Only 10,000 Romans escaped, with the rest either killed or captured. The battle came to be seen as evidence of Hannibal's genius for tactical generalship, while it was among the worst defeats suffered by Ancient Rome.

Ancient Rome: During the Gallic Wars, in 52 BC Roman commander Julius Caesar attempted to engage the forces of tribal leader Vercingetorix in open battle in what is now central France. Vercingetorix kept the River Elave (now Allier) between Caesar's forces and his own. His troops destroyed or removed the bridges and mirrored the movements of Caesar's troops, preventing Caesar from crossing the river. Caesar responded by hiding forty of his sixty cohorts and arranging the remaining twenty to give the appearance of sixty as viewed from the opposite riverbank. The twenty cohorts continued to march along the river, and Vercingetorix's troops continued to mirror their movements. Caesar then led the forty hidden cohorts back to a repairable bridge, had it fixed, led his troops across, and sent for the other twenty cohorts to rejoin him. Now on the same side of the river as Vercingetorix, Caesar was able to engage the Gallic tribes in battle as he intended.

Mongol Empire: The Mongol Empire frequently used deception to aid its military success. A favored tactic was to exaggerate the size of their army, which would cause their enemies to surrender or flee. When he fought the Naimans in 1204, Chinggis Khan ordered his soldiers to light five campfires each, giving the impression of a more numerous army. In 1258 Möngke Khan invaded Sichuan with 40,000 soldiers, and spread rumors of 100,000 in an effort to intimidate his enemy.
When confronting numerically superior forces, the Mongols often sent troops behind their own lines to raise dust with branches tied to their horses' tails, which created the impression that reinforcements were en route. Mongol soldiers had more than one horse each, and to exaggerate the size of their army, they would compel prisoners or civilians to ride their spare horses within sight of the enemy, or mount dummies on their spare horses. To make their forces appear smaller, the Mongols would ride in single file, minimizing dust and making the hoofprints of their horses more difficult to count. Mongol armies also used the feigned retreat. A typical tactic was to deploy the mangudai, a vanguard unit that would charge the enemy, break up its formation, and then fall back in an attempt to draw the enemy into a position more favorable to the Mongols.

Middle Ages: Examples of deception occurred during the Crusades. In 1271, Sultan Baybars captured the formidable Krak des Chevaliers by handing the besieged knights a letter, supposedly from their commander, ordering them to surrender. The letter was fake, but the knights believed it was genuine and capitulated.
In 1401, during the Glyndŵr Rising, the Tudors of Wales were seeking a revocation of the price that Henry Percy had placed on their heads. After deciding to capture Percy's Conwy Castle, one member of the Tudor faction posed as a carpenter, gained access, and then admitted his compatriots. The successful deception was in part responsible for the creation of England's Tudor dynasty.

Renaissance: In an event from the early 1480s that was recounted in Washington Irving's Conquest of Granada, during the Granada War, the Alhama de Granada was besieged by Moors. During the siege, a portion of the fortress' outer wall was destroyed after the earth beneath it was washed away in a violent storm. To conceal the breach, the Conde de Tendilla, leader of the Spanish defenders, directed the erection of a cloth screen. The screen deceived the Moors because it was painted to resemble stone, and no Moorish besiegers ventured close enough to spot the fakery. The wall was repaired over the next several days, and the Moors did not learn of the gap in the Alhama's defenses.
Henry VIII of England led troops on the European mainland during the War of the League of Cambrai. On 4 September 1513, Henry's forces began to besiege the city of Tournai in what is now Belgium. The site of a thriving tapestry industry and home to many well-known painters, Tournai prolonged the siege by using painted canvas that resembled trenchworks to exaggerate the strength of its defenses. As a result of this deception, the city held out for several days longer than expected and obtained favorable terms when it surrendered.

Colonial Africa: In 1659, the kingdom of Denmark–Norway constructed Fort Christiansborg near what is now Accra in Ghana. Used to control commerce in slaves, as well as raw materials including gold and ivory, the site changed hands several times between Denmark–Norway, Portugal, and Sweden, sometimes by force, sometimes by purchase. In 1692, Nana Asamani, the king of the Akwamu people, planned to capture the fort from Denmark–Norway. Disguising himself as a cook and interpreter, he obtained work at the fort, where over the next year he became proficient in the Danish language and conducted reconnaissance to learn about the activities of the facility's occupants and the people with whom they traded.
After gaining familiarity with Fort Christiansborg's occupants and operations, in 1693 Asamani informed the Danish traders who occupied it about a group of Akwamu who desired to purchase weapons and ammunition, and suggested they were so anxious to buy that the Danes should inflate their prices. Lured by the prospect of large profits, the Danes bartered with the 80 Akwamu that Asamani had brought to the fort. When the Danes allowed the Akwamu to inspect rifles and prepare to test-fire them, the Akwamu instead used the guns to commence an attack on the Danes. Caught by surprise, the Danes were quickly overpowered and ejected from Fort Christiansborg. The Akwamu occupied the post for a year before Asamani agreed to sell it back to Denmark–Norway. Asamani kept the keys as a trophy, and they are still in the possession of the Akwamu.

French and Indian War: During the Seven Years' War in North America (known in the United States as the French and Indian War), British commander James Wolfe attempted throughout the summer of 1759 to force French commander Louis-Joseph de Montcalm to come out of his well-defended position in Quebec City. When artillery fire that destroyed most of the city did not produce the desired effect, Wolfe employed a deception strategy called "uproar east, attack west" Wolfe ordered Admiral Charles Saunders to move the British fleet on the Saint Lawrence River to a position opposite one of Montcalm's main camps east of Quebec City. This demonstration gave the appearance of preparations for an upcoming attack. Montcalm was deceived, and moved troops to guard against a British assault from that location.
Wolfe's soldiers at Quebec City capitalized on the favorable balance of forces created by the deception. First, they opened a road from the riverbank to the city heights. Next, they deployed into battle formation on a farmer's field near the city walls. Caught by surprise, Montcalm knew he would not be able to withstand a siege and had no choice but to fight. On 13 September 1759, the French were decisively beaten in the Battle of the Plains of Abraham. The loss of Quebec led to defeat in the war and France was forced to cede Canada to the British.

American Revolution: 

Siege of Boston: As head of the Continental Army, George Washington successfully used deception to equalize the odds in the fight against the larger, better-equipped, and better-trained British army and its mercenary allies. During the Siege of Boston from April 1775 to March 1776, the newly organized Continental Army suffered from numerous equipment and supply shortages. Among the most critical was a lack of gunpowder, which was so acute that in a battle, Washington's troops would be able to fire no more than nine bullets per man. To conceal the lack of gunpowder from the British, Washington's quartermaster soldiers filled gunpowder casks with sand and shipped them from Providence, Rhode Island to the Continental Army's depots. The deception fooled British spies, and British commanders decided not to risk an attack during the siege.

Battle of Long Island: After the Patriot defeat at the Battle of Long Island in late August 1776, Washington's forces retreated to Brooklyn Heights, with a superior British force surrounding them on three sides and their backs to the East River. The British expected Washington would find his position untenable and surrender. Washington instead arranged for a flotilla of small boats to ferry his 9,000 troops across the river to the relative safety of Manhattan Island. Moving under cover of darkness, Washington's troops withdrew unit by unit to avoid the appearance that a general retreat was taking place.