Battle of Vlotho

The Battle of Vlotho was fought on 17 October 1638. It was a victory for the Imperial Army under the command of Field Marshal Melchior von Hatzfeldt, and ended the attempt by Charles I Louis, Elector Palatine, to recapture the Electoral Palatinate. Charles Louis' defeat marked the last time either Palatine or English forces played a significant role in the Thirty Years' War.
Background.
Frederick V, the Winter King, had died in 1632. The desire to recover the Palatinate, which had sparked English intervention in the Thirty Years' War in the previous years was at this point disregarded by most. In 1638 Charles Louis, 2nd son and heir of Frederick made one last attempt to recover his territories. Choosing as his base of operations the town of Meppen, on the Münster-East Frisian frontier, he raised a force of 4,000 men using English gold. Alongside Charles Louis were his brother Prince Rupert and a company of English gallants dedicated to the Winter Queen, including Lord Craven, and the Earl of Northampton.
To assist Charles Louis, the commander of the Swedish army Johan Banér sent Charles Louis a 1,000 strong detachment, under the command Lieutenant-General James King (a Scot who had commanded the Swedish left wing at the Battle of Wittstock in 1636). Many of these were British, such as Colonel William Vavasour.
The original plan was to form the army in Westphalia and then to advance through Hesse and to retake the Palatine. However Banér considered this to be unrealistic and persuaded the participants that they should start by besieging and capturing Lemgo, ostensibly to secure their lines of communication, but it also suited the wider war aims of the Swedes because whatever else happened during the campaign it would be a concrete loss for Banér's enemies and a gain for him.
On 15 October 1638 the Palatine-Swedish army started to besiege Lemgo, and the Imperial Field Marshal Melchior von Hatzfeldt—who had been assigned to command Imperial forces in Westphalia after his defeat at Wittstock, immediately started to assemble a relief force.
The next day this approaching force was detected by Palatine-Swedish vedettes who estimated it to be 8,000 strong, so their commanders decided to raise the siege and retreat to the Swedish fortress at Minden. The Palatines had two possible routes to Minden, they chose to take the road to Vlotho, which was shorter, but also meant that they remained on the same side of the river Weser as the Hatzfeldt. Their major problem was that whatever route they took, unless they abandoned their artillery and baggage train, Hatzfeldt's unencumbered force was going to catch up with them.
The battle.
The faster Imperial force managed to outpace the Palatines and cut off their path at Vlotho bridge.
The Palatines had ordered their marching column with the baggage at the front, followed by their cavalry, with the infantry and artillery at the rear. King formed the Palatine cavalry up in a defensive line on the Eiberg hillock and set off to bring up the infantry. 
After King had left, his subordinate Hans von Königsmarck suggested that rather than wait for their infantry, they could send their cavalry forward up a narrow valley which would act as a defile and prevent Hatzfeldt from concentrating his forces against them. Charles Louis and Craven agreed to the plan. Three cavalry regiments under the command of Königsmarck were sent forward up the defile one behind the other, while the dragoons and the two commanders remained on the hillock awaiting the arrival of their infantry.
As soon as he saw what the Palatine cavalry was doing, Hatzfeldt ordered two of his own cavalry regiments to advance down the valley to meet the enemy. He sent a further 800 on a flanking attack, concealed by the low hills around the valley.
In the clash that followed the two leading Palatine regiments broke. The third regiment was commanded by Prince Rupert who, in an early example of a manoeuvre he would become famous for in the English Civil War, ordered a flat out charge. Hatzfeldt's cavalry were driven out of the valley. As Rupert's cavalry debouched from the defile they were hemmed in by Hatzfeldt's superior forces. Craven led the Palatine reserves — two regiments of dragoons — up the defile to support Rupert's attack, but the Imperial cavalry sent to flank the attackers closed in from behind to envelop Rupert's cavalry and Craven's reinforcements.
The position was now hopeless, and rather than reinforce failure, Königsmarck withdrew with his Swedish cavalry. Before surrendering, Rupert's and Craven's soldiers held on long enough to allow King to withdraw all the Swedish contingent in good order, but the battle was lost.
Charles Louis tried to escape in his coach but it sank in the Weser. He survived by clutching a branch and managed to return to his Dutch exile.
Aftermath.
In the opinion of William Guthrie:
The defeat was the last gasp of the Palatine cause and English intervention in the war. Soon the start of the English Civil War prompted the return of most British soldiers and officers.