With forces that eventually numbered about 8,000, Gálvez, assisted by Spanish and French naval forces, first blockaded the Pensacola harbour, and then began siege operations on 9 March. By the 30 April the Spanish had successfully placed cannons that could fully attack the main Pensacola defences. A lucky cannon shot hit the powder magazine in one of the outer defences on 8 May, and the Spanish quickly capitalised upon this development by capturing the British position.