From 1586, Walsingham received many dispatches from his agents in mercantile communities and foreign courts detailing Spanish preparations for an invasion of England. Walsingham's recruitment of Anthony Standen, a friend of the Tuscan ambassador to Madrid, was an exceptional intelligence triumph and Standen's dispatches were deeply revealing. Walsingham worked to prepare England for a potential war with Spain, in particular by supervising the substantial rebuilding of Dover Harbour, and encouraging a more aggressive strategy. On Walsingham's instructions, the English ambassador in Turkey, William Harborne, attempted unsuccessfully to persuade the Ottoman Sultan to attack Spanish possessions in the Mediterranean in the hope of distracting Spanish forces. Walsingham supported Francis Drake's raid of Cadiz in 1587, which wrought havoc with Spanish logistics. The Spanish Armada sailed for England in July 1588. Walsingham received regular dispatches from the English naval forces, and raised his own troop of 260 men as part of the land defences. On 18 August 1588, after the dispersal of the armada, naval commander Lord Henry Seymour wrote to Walsingham, "you have fought more with your pen than many have in our English navy fought with their enemies".