Although the salary was low, Hay was interested in serving in Madrid both because of the political situation there—Queen Isabella II had recently been deposed—and because the U.S. Minister was the swashbuckling former congressman, General Daniel Sickles. Hay hoped to assist Sickles in gaining U.S. control over Cuba, then a Spanish colony. Sickles was unsuccessful and Hay resigned in May 1870, citing the low salary, but remaining in his post until September. Two legacies of Hay's time in Madrid were magazine articles he wrote that became the basis of his first book, "Castilian Days", and his lifelong friendship with Sickles's personal secretary, Alvey A. Adee, who would be a close aide to Hay at the State Department.