During 1652, Milton suffered a number of traumatic events. First, his eyesight, which had been growing weaker, gave out completely, probably because of glaucoma. By 1652, Milton was totally blind. Second, his young son, John, (b. 1651) died under mysterious circumstances. Third, his wife died from complications in giving birth to the Milton's third daughter, Deborah. And fourth, Pierre du Moulin published the pamphlet Regii Sanguinis Clamor (Outcry of the King's Blood), a pro-Charles pamphlet to which Milton was ordered to reply. Milton's reply was entitled Defensio Secunda, which was published in 1654. By that time, Andrew Marvell, Milton's friend and fellow poet, was working as his assistant. Milton was also allowed to cut back on his official labors and to use an amanuensis (akin to a secretary) as an aide.
Even with his personal and physical problems, Milton continued to write. His major personal project in the 1650s was De Doctrina Christiana, a work in which he tried to state formally all of his religious views. In 1656, he married Katherine Woodcock, who died two years later. He would marry for the third time in 1663 to Elizabeth Minshull, who became his nurse as his health declined in his later years.
