The use of McNabs Island for military purposes was first considered in 1711 when DeLabat explored the possibility of fortifying Maugher Beach to protect the harbour and planned settlement on the island. Before either the settlement or fortification were constructed, however, Great Britain acquired mainland Nova Scotia from France under terms of the Treaty of Utreacht.

The British first seriously considered fortifications on McNabs Island in 1762 after France captured St. John's. Although 200 men of the Provincial Regiment began clearing brush and underwood at Ives Point in order to construct an artillery battery, the orders were soon rescinded.

In the early years of Halifax there was no magazine to store the military's gun powder. As a result, the gun powder was kept in a vessel anchored near the north end of McNabs Island. In 1812, a huge mooring chain with anchors was laid off the northern end of McNabs Island. From this chain the magazine ship was moored.