The British military occupied the Danish West Indies from 1801 until April of 1802, when, with the dissolution of the Armed Neutrality Pact at the Treaty of St. Petersburg the islands were returned to Denmark. During the Napoleonic Wars, 1803-1815 the British occupied the Danish West Indies a second time, in 1807. During both periods, British troops headquartered themselves on Hassel Island, noting the defensive location of the land (still a peninsula at this time) and desiring the separation from the “unclean” town of Charlotte Amalie. During the first occupation, at least 2 companies of black slave soldiers, members of British West India Regiments, were stationed on Hassel Island. Under the command of British Lieutenant General Thomas Trigge and Lieutenant Colonel Charles Shipley, the occupying troops utilized Danish fortifications and further developed the island throughout the years with more than 30 new military structures.
After the Napoleon was defeated, the British returned the islands to Denmark on April 5th, 1815. The long period of war and occupation negatively affected the once flourishing economy of St. Thomas. The Danish government now took control of the fortifications on Hassel Island and private land ownership was restored to the Hazzell family.