Fort King George crowns the ridge above Scarborough, where Tobago's colonial rulers competed for control of the island and its plantation economy. British forces began fortifying the position in the 1770s as Tobago changed hands during the long eighteenth-century struggle among European empires. The site commanded the harbor and sea approaches, allowing artillery to protect Scarborough and the shipping that connected sugar estates with Atlantic markets. Its military history cannot be separated from the labor of enslaved Africans whose forced work sustained the wealth the fort was intended to defend.

In June 1781, during the American Revolutionary War, French forces captured Tobago from Britain. French governor General Blanchelande began major construction on the hill in 1784. Work paused and then resumed in 1786 under Count Arthur Dillon. The expanding stronghold was named Fort Castries, honoring the French minister of marine. Its barracks, magazines, gun positions, officers' quarters, and supporting structures formed a defensible complex overlooking the colonial capital. Political upheaval in France soon echoed in the Caribbean garrison. The fort was renamed Fort République in 1789 and Fort Liberté in 1790, when soldiers mutinied amid revolutionary tensions.

Britain recaptured Tobago and the fort in 1793 during the wars of the French Revolution. The Treaty of Amiens returned the island to France in 1801, but renewed war brought another British conquest in 1803. In 1804 the installation received the lasting name Fort King George in honor of George III. These rapid transfers demonstrate Tobago's strategic importance and the instability of Caribbean sovereignty: flags, commanders, and official names changed while the fortified hill remained essential to whoever controlled the island.

Under permanent British rule, the post housed troops who guarded Scarborough and enforced colonial authority. Soldiers lived in barracks, stored powder in protected magazines, maintained cannon, and used prison cells and a bell tank that collected or stored water. The garrison's presence supported a society based on slavery until British emancipation in the 1830s and then on other unequal labor systems. A devastating hurricane on 11 October 1847 damaged or destroyed many buildings. Although a garrison remained until 1854, the fort's active military role declined as imperial defense needs changed.

Surviving structures were later restored or reconstructed, and the former Barrack Guard House became home to the Tobago Museum. Cannon, magazines, officers' quarters, and military artifacts now interpret the repeated contests for the island. Indigenous objects and colonial documents broaden the story beyond the garrison itself. Fort King George is one of Tobago's most intact historic fortifications because its commanding location and masonry remains still reveal how the complex operated. It preserves evidence of Anglo-French warfare, revolutionary unrest, plantation slavery, emancipation, hurricane destruction, and the eventual conversion of an instrument of empire into a public heritage site. Control of Tobago changed repeatedly among European powers, and the fort's changing name and armament reflected those contests. Its garrison also depended on enslaved and free laborers who supplied, repaired, and maintained the position. Interpreting the site therefore requires attention to colonial warfare and to the unequal society that made fortification possible.