The leadership of the Duke of Hamilton proved to be poor and his army was so ill provided for that as soon as England was invaded it began to plunder the countryside for sustenance. On 8 July the Scots, with Langdale leading an advance guard, were near Carlisle, and reinforcements from Ulster were expected daily. Lambert's cavalry were at Penrith, Hexham and Newcastle, too weak to fight and having only skillful leading and rapidity of movement to enable them to gain time. Appleby Castle surrendered to the Scots on 31 July, whereat Lambert, who was still hanging on to the flank of the Scottish advance, fell back from Barnard Castle to Richmond so as to close Wensleydale against any attempt of the invaders to march on Pontefract. All the restless energy of Langdale's cavalry were unable to dislodge Lambert from the passes or to find out what was behind that impenetrable cavalry screen. The crisis was now at hand. Cromwell had received the surrender of Pembroke Castle on 11 July, and had marched off, with his men unpaid, ragged and shoeless, at full speed through the Midlands. Rains and storms delayed his march, but he knew that the Duke of Hamilton in the broken ground of Westmorland was still worse off. Shoes from Northampton and stockings from Coventry met him at Nottingham, and gathering up the local levies as he went, he made for Doncaster, where he arrived on 8 August, having gained six days in advance of the time he had allowed himself for the march. He then called up artillery from Hull, exchanged his local levies for the regulars who were besieging Pontefract, and set off to meet Lambert. On 12 August he was at Wetherby, Lambert at Otley, Langdale at Skipton and Gargrave, Hamilton at Lancaster, and Sir George Monro with the Scots from Ulster and the Carlisle Royalists (organized as a separate command owing to friction between Monro and the generals of the main army) at Hornby. On 13 August, while Cromwell was marching to join Lambert at Otley, the Scottish leaders were still disputing whether they should make for Pontefract or continue through Lancashire so as to join Lord Byron and the Cheshire Royalists. Battle of Preston On 14 August 1648 Cromwell and Lambert were at Skipton, on 15 August at Gisburn, and on 16 August they marched down the valley of the Ribble towards