The siege of St. Augustine began when English colonists from Carolina, commanded by Colonel James Moore, launched an offensive against the Spanish fortification in St. Augustine, Florida. This city, founded in 1565, was the oldest continuously inhabited European-established settlement within the continental United States and served a vital role as a Spanish military stronghold in North America. The siege was driven by territorial ambitions, as the British sought to expand their influence in the region, particularly during the larger conflict known as Queen Anne's War, which saw the British and Spanish fighting for control over North American territories, Caribbean islands, and parts of Europe.

Col. James Moore assembled a significant force of nearly 1,000 men, including regular soldiers, militia, and allied Native American tribes, to encircle St. Augustine. The Spanish garrison, led by Governor Manuel de Montiano, was much smaller and primarily composed of soldiers and local militia, tasked with defending the fort. For several months, the English colonists besieged the city, employing artillery and other tactics to attempt to breach its defenses. The duration of the siege was marked by skirmishes, supply shortages, and challenges to both sides as the defenders fought vigorously to protect their territory.

Despite the initial advantages, the siege did not achieve a decisive victory for the English forces. The Spanish relief army, which included reinforcements from Havana, ultimately broke the siege and restored the garrison's strength. The failed siege ended with a retreat by Moore's forces, which would have implications for the military strategies and colonial relations in the years to come. While the siege did not result in a change of control over St. Augustine, it highlighted the ongoing competition for dominance in colonial America and the significance of Florida as a battleground for power between European colonial empires.