The earliest record of a fortification here dates to 1680, when one gun stood on the headland. Vazon Bay was an obvious landing beach for any French invader, and the British and Guernsey authorities knew it. After the French nearly took Jersey in 1781, defences across both bailiwicks were rushed forward. By 1795 the position had been improved with additional gun pads. By 1805 there were six guns on Hommet. The road from St Peter Port out to the fort was upgraded to military standard around 1808, partly funded by the sale of land reclaimed from the Braye du Valle marshes - one of John Doyle's many ingenious civil engineering projects.

The Martello tower at the heart of Fort Hommet went up in 1804, during the Napoleonic Wars and during the tenure of Lieutenant Governor John Doyle. Doyle, never a man to wait for paperwork, sidestepped the Royal Ordnance Corps entirely by classifying the construction as 'field works' and hiring a local builder named Gray to put up the tower along with two others. The three Guernsey Martellos - Fort Hommet, Fort Grey, and Fort Saumarez - are smaller than their cousins on the English coast. Each was meant as a keep at the heart of an open gun battery, with a single 24-pounder carronade on the roof. Hommet and Saumarez share an unusual feature: an exterior staircase climbing to the second floor.

The Victorian army updated the fort to match its new artillery. In 1852, the 24-pounders were replaced in some batteries with 68-pounders and eight-inch shell guns. Barracks went up. Magazines were enlarged. The headland kept gathering iron. In World War II, after Guernsey was demilitarized and surrendered to German forces in June 1940, Fort Hommet became Stützpunkt Rotenstein - 'red stone strongpoint.' The Wehrmacht added a reinforced personnel shelter, a coastal-defence gun casemate, trenches, machine-gun pits, a Czech ZB-53 machine gun mounted in a steel ball, and a ring of minefields around the headland. The Martello tower itself, built to shoot at the French, was incorporated into a system pointed at the British.

When liberation came in May 1945, the British Army and the islanders went to work on the German structures with hammers and scrap-metal hopes. By the late 1940s the guns, blast doors, and metal fittings were gone. Many of the bunkers - including the Fort Hommet gun casemate - were buried under earth in an attempt to give the coastline back its pre-war shape. For decades they sat under turf, invisible. More recently the States of Guernsey has dug parts of the complex out again. The Fort Hommet 10.5 cm Coastal Defence Gun Casement Bunker is now open to visitors, on restricted hours. The M19 Maschinengranatwerfer bunker - a German automatic mortar emplacement - has been restored too. On 2 November 1990 the whole site, Martello tower and German concrete alike, was listed as a Protected Monument.