On June 23rd, 2016, the United Kingdom conducted a referendum to determine the will of its people to remain in the European Union or to withdraw from it. The results were 16,141,241, or 48.11%, to remain, and 17,410,072, or 51.89% to exit. The following day Prime Minister David Cameron, who supported the "Remainers" in spite of his membership in the Conservative Party which supported the "Brexiters", announced his intention to resign. On July 13th, Theresa May, another Conservative, became Prime Minister. On March 29th, 2017, Prime Minister May triggered Article 50 which began the two-year clock leading up to the United Kingdom's total withdrawal from the EU. On March 31st Spain announced its intention to exercise some degree of control over Gibraltar, which was inferred to include the possibility of re-annexation. On April 2nd Michael Fallon, the UK's Defense Secretary, announced that he would be prepared to go to war with Spain over Gibraltar. The UK's War Plan included the possible threat of blockading the Strait of Gibraltar using the Royal Navy's vessels stationed in Gibraltar supplemented by warships and aircraft from the British Isles. Such a closure would restrict travel from the Atlantic to the Mediterranean and the key EU ports of Valencia, Piraeus, Istanbul, Genoa, and Barcelona. The only other oceanic entrance to the Mediterranean would be through the Suez Canal in Egypt. EU countries' economies could be in ruin before the war was over.