Those unexpected impediments, which always embarrass military movements conducted by men without experience, having delayed the arrival of his northern troops, Oglethorpe entered Florida at the head of his own regiment, aided by a party of Indians; and invested Diego, a small fort about twenty-five miles from St. Augustine, which capitulated after a short resistance. He then returned to the place of rendezvous, where he was joined by colonel Vanderdussen, and by a company of Highlanders under the command of captain M'Intosh; a few days after which, he marched with his whole force, consisting of about two thousand men, to fort Moosa, in the neighbourhood of St. Augustine, which was evacuated on his approach. The general now perceived that the enterprise would be attended with more difficulty than had been anticipated. In the time which intervened between his entering Florida and appearing before the town, supplies of provisions had been received from the country, and six Spanish half gallies carrying long brass nine pounders, and two sloops laden with provisions, had entered the harbour. Finding the place better fortified than had been expected, he determined to invest it completely, and to advance by regular approaches. In execution of this plan, colonel Palmer, with ninety-five Highlanders, and forty-two Indians, remained at fort Moosa, while the army took different positions near the town, and began an ineffectual bombardment from the island of Anastasia. The general was deliberating on a plan for forcing the harbour and taking a nearer position, when colonel Palmer was surprised, and his detachment cut to pieces. At the same time some small vessels from the Havanna, with a reinforcement of men and supply of provisions, entered the harbour through the narrow channel of the Matanzas.
The army began to despair of success; and the provincials, enfeebled by the heat, dispirited by sickness, and fatigued by fruitless efforts, marched away in large bodies. The navy being ill supplied with provisions, and the season for hurricanes approaching, captain Price was unwilling to hazard his majesty's ships on that coast. The general, labouring under a fever, finding his regiment, as well as himself, worn out with fatigue, and rendered unfit for action by disease; reluctantly abandoned the enterprise, and returned to Frederica.