By this point, relations between Francis and Henry VIII were collapsing. Henry—already angered by the French refusal to pay the various pensions, which were owed to him under the terms of past treaties—was now faced with the potential of French interference in Scotland, where he was entangled in the midst of an attempt to marry his son to Mary, Queen of Scots, that would develop into the open warfare of the "Rough Wooing". He had intended to begin a war against Francis in the summer of 1543, but negotiating a treaty to that effect with the Emperor proved difficult; since Henry was, in Charles's eyes, a schismatic, the Emperor could not promise to defend him against attack, nor sign any treaty which referred to him as the head of the Church—both points upon which Henry insisted. Negotiations continued for weeks; finally, on 11 February 1543, Henry and Charles signed a treaty of offensive alliance, pledging to invade France within two years. In May, Henry sent Francis an ultimatum threatening war within twenty days; and, on 22 June, at last declared war.