It was a deal the United States made with Britain before they entered World War II which gave the British 50 old destroyer ships for US right to build ports in the Caribbean.

(1940) A World War II agreement between F. D. Roosevelt and Churchill. Known as the Destroyer Transfer Agreement, it ensured the US transfer to Britain of 50 much-needed destroyers in exchange for leases of bases in British possessions in the West Indies, New-foundland, and British Guiana. Being of World War I design, the destroyers became surplus to British requirements during the war, but in the early and critical stage of World War II they were an invaluable supplement to available escort vessels.

If you are referring to World War II, it was 3 September 1941

During World War II, British soldiers and civilians referred to Americans as yanks - from Yankees. The Americans called the British limeys.

The British leased bases in the Caribean to the US in exchange for 50 obsolete destroyers. Lend-Lease was vital to the British in defence of atlntic convoys.

Following World War II, Bulgaria was controlled by the Soviet Union.