 By an ancillary secret convention, Spain committed to making preparations for war against Britain.Britain first declared war against Spain on 4 January 1762, and on 18 January 1762, Spain issued their own declaration of war against Britain.On 6 January 1762, the British Cabinet led by Prime Minister John Stuart, agreed to attack Havana in the West Indies, and approved Colonel William Draper's scheme for taking Manila with his forces, which were already in the East Indies.