On 9th July 1643 Sir William Waller, the Roundhead commander in the West of England, besieged the Wiltshire town of Devizes. The Royalist commander, Sir Ralph Hopton sent men to nearby Oxford for help. Hopton stayed in Devizes to defend the town. On Hopton’s orders Prince Maurice, Lord Hartford and three hundred cavalry rode through the night to Oxford, only to find that most of the King’s army had left the city to fight in the Midlands. But the king had already sent a brigade of cavalry to Devizes, under the command of Lord Wilmot. There was also a spare brigade of cavalry in Oxford led Lord John Byron. Byron and his cavalry rode to Devizes.
Devizes had come under attack. Hopton had sent cavalry to fight the Roundheads but the cavalry had been beaten, scattered and much of their ammunition captured. The Roundheads tried to capture Devizes but Hopton’s infantry drove them out. Sir William Waller attempted to negotiate Devizes surrender. Hopton pretended to agree to the terms of surrender but was only playing for time until help arrived.
On July 13th Byron, Wilmot and the defeated Royalist cavalry from Devizes met up at the town of Marlborough. They rode toward Devizes to fight Waller’s army. The two armies met at Roundway Down. Waller’s Roundhead’s were positioned on the high ground. They numbered 5,000. Half were infantry, half were cavalry. Many of their cavalry were cuirassiers who were dressed from head to toe in bullet proof armour. The Roundheads had ten cannons. The Royalist numbered 1,500 cavalry. They had no infantry and two cannons.
At the beginning of the battle small units of cavalry (called the forlorn hope) fought each other. The Cavaliers did well enough for Wilmot to order a full-blooded cavalry charge. Wilmot attacked the cuirassiers. The cuirassiers rode in the way of their cannons, which couldn’t fire for fear of hitting their own men. Despite their armour, Wilmot defeated the cuirassiers. Byron charged uphill to join Wilmot. Byron chased the rest of the enemy cavalry from the battlefield. Waller’s infantry were now alone and without support. Roundhead musketeers formed squares and fought off charge after charge from the enemy horse. The cavaliers captured the Roundhead cannons and fired them at the enemy musketeers. Infantry from Devizes left the town and joined the battle. The Roundhead army was in chaos. It was every man for himself as the Roundheads ran away.
In two to three hours, the cavaliers had beaten an army twice their size. Roundway Down was the most one-sided defeat ever suffered by Parliament during the Civil War. The victory allowed the Royalists to take control of the South West of England.