Great as was the triumph of the revolt in Brazil, it at first filled the heart of the King of Portugal with alarm, for it deprived him of an ally in Europe on whose valuable assistance he had firmly relied. Everywhere he looked in vain for help. Sweden could do nothing; England was torn by civil war; and in France his ally, Cardinal Richelieu, had been succeeded as supreme minister by Cardinal Mazarin. John IV. instinctively felt that he could not depend upon Mazarin, who would certainly throw him over, if a peace should be made between France and Spain, and in his despair he made an offer to resign his throne to a French prince, who should bring ample assistance from France. The nature of this offer is best told in a letter from Mazarin to the Duke of Longueville, dated October 4, 1647. "The King of Portugal," wrote the Cardinal, "after having maturely considered the state of affairs, is disposed to resign his crown and retire to the Azores, and to offer his kingdom to any one whom the Queen of France shall select, believing himself strong enough to have such a person recognized as king and obeyed by all the people of Portugal. He only desires that the person selected should be a prince who may expect powerful help from France, and that he shall have the means to make such an alliance with his eldest son, as may eventually secure the succession of the kingdom to the latter. He proposes M. the Duke of Orleans and Mademoiselle, or M. the Prince, or you and your daughter."[29] This strange offer of abdication came to nothing, and it may well be doubted if John IV. would have had the power to introduce a foreign prince in this way; and if he had succeeded, Mazarin would have abandoned Portugal with equal certainty even if a French prince had been on its throne. Though this scheme failed, John IV. still hankered after help from France; he offered his daughter, Donna Catherine de Braganza with a large dowry both to the Duke of Beaufort and to the young Louis XIV., and he also promised large sums of money to the avaricious cardinal for his own use. Years passed on, occupied with these various schemes and entreaties for assistance, and it was not until John IV. threatened to make peace at any price with Philip IV. that Mazarin's trusted agent, the Chevalier de Jant, signed an offensive and defensive alliance with Portugal on September 7, 1655.[30]