of Savoy, defeated the French in the Battle of St. Quentin (1557) (10–27 August). The Spanish attempted to blockade Rome by occupying the port of Ostia but were driven back by the Papal armies in a surprise attack. However, when French troops were unable to come to their aid, the Papal armies were left exposed and were defeated, with Spanish troops under the Duke of Alba arriving at the edge of Rome. Out of fear of another sack of Rome, Paul IV agreed to the Duke of Alba's demand for the Papal States to declare neutrality by signing the Peace of Cave-Palestrina (12 September 1557). Emperor Charles V criticized the peace agreement as being overly generous to the Pope. English entry and Gravelines A brief French-backed revolt led by Thomas Stafford against queen Mary I of England resulted in a three-day siege of Scarborough Castle in April 1557. Mary declared war on France in June 1557 and made a minor contribution to the Hispano-Savoyard victory at St. Quentin in August. But England's entry into the war provoked the French Siege of Calais in January 1558, which the English lost. French armies plundered Spanish possessions in the Low Countries and emerged victorious in the Siege of Thionville (April–June 1558). Nonetheless, Henry lost gravely at the Battle of Gravelines (13 July 1558) and was forced to accept a peace agreement in which he renounced any further claims to Italy. The wars ended for other reasons, including "the Double Default of 1557", when the Spanish Empire, followed quickly by the French, defaulted on its debts. In addition, Henry II had to confront a growing Protestant movement at home, which he hoped to crush. Military technology Oman (1937) argues that the inconclusive campaigns which generally lack a decisive engagement were largely due to ineffective leadership and lack of offensive spirit. He notes that mercenary troops were used too often and proved unreliable. Hale emphasizes the defensive strength of bastion forts newly designed at angles to dissipate cannon fire. Cavalry, which had traditionally used shock tactics to overawe the infantry, largely abandoned it and relied on pistol attacks by successive ranks of attackers. Hale notes the use of old-fashioned mass formations, which he attributes to lingering conservatism. Overall, Hale emphasizes new levels of tactical proficiency. Finance In 1552 Charles V had borrowed over 4 million ducats, with the Metz campaign alone costing 2.5 million ducats.