In 1620 the Spanish Monarchy entered the Thirty Years' War with the intention of conquering the Electoral Palatinate. The Spanish saw this as necessary because the Palatinate lay on the route from Italy to the Spanish Netherlands. Also, Spain was Catholic, so they naturally supported the Holy Roman Emperor against the Protestants in the Thirty Years' War. In August 1620, Don Ambrosio Spinola, as commander-in-chief of the Army of Flanders, invaded the Palatinate from the Spanish Netherlands and advanced over Frankfurt. The rapid relief introduced in this city by the Protestants dissuaded him from attack, and Spinola decided march to Oppenheim. In early September the towns of Bad Kreuznach and Alsheim were captured by the Spaniards. The primary objective of Spinola was to occupy a city of some entity that would allow secure their supplies and ammunition, thus anticipating the arrival of winter. The attention of the Marquis focused on Oppenheim, a town of strategic importance because their bridge guarded the entrance to the heart of the Electorate of the Palatinate. The town, however, was strongly garrisoned and was protected by strong fortifications, so an immediate assault was seen as an option inadvisable.
Capture of Oppenheim
Spinola raised his camp at Alsheim, and performed a great maneuver of distraction, simulated a march over Worms to distract the forces of the Protestant Union. Joachim Ernst, Margrave of Brandenburg-Ansbach, who commanded the Protestant army stationed in Oppenheim and surroundings, about 24,000 soldiers, took the bait and went with most of his troops to Worms, leaving a small garrison in Oppehneim. Spinola, between therefore, taking advantage of the night approached to Oppenheim, where he arrived with his army to dawn on 14 September, and the assault on the positions of the town not long in coming. by Joannes Janssonius. The Protestant garrison, seeing such formidable army, forsook their defenses in a hurry, and soon surrendered without suffering more than a few killed by the assailants. According to the correspondence of Spinola, the Protestant garrison consisted of 800 strong musketeers recruited in the Palatinate. Oppenheim was captured and the Protestant soldiers were disarmed and released. Besides several flags, the Spanish seized the baggage of Protestant soldiers in the barracks of the town.
Consequences
The loss of Oppenheim was a severe blow to the Palatinate, as the town was a key to dominate the shore of Rhine, because their bridge, guarded the entrance to the heart of the Palatinate. The bridge had been destroyed and Spinola ordered rebuild it. Also sent to reinforce the defenses and established his ammunition dump. The various garrisons that had been left in the conquered places had driven down the number of the Spanish army, so that Spinola decided quartered in Oppenheim, and requested reinforcements to Archduke Albert in Brussels. On 25 September, there was a council of the principal officers of the Spanish army, and that day it was learned that the Protestant cavalry were preparing an attack on their barracks. Spinola dispatched to Count Hendrik van den Bergh, in command of 2,200 cavalry, the regiment of the Count of Henden and 3 cannons, to ambush, but the fight did not occur. At the onset of winter, the two opposing armies withdrew to their garrisons. By then, the Protestants had already received the expected reinforcements from England led by Sir Horace Vere. In the six months following, the Spaniards captured more than 30 towns and castles along the Lower Palatinate.
