In January 1547, the imperial colonel and mercenary leader Christoph von Wrisberg recruited men in Münsterland. Via the Prince-Bishoprics of Osnabrück and of Minden, which were still loyal to the emperor, Wrisberg's army marched to Bremen to begin besieging the city. In April the 19-year-old Duke Eric II joined the besieging army, which numbered 12,000 men with Eric's reinforcements. In May, Eric was informed that a Protestant army was pillaging and plundering his Principality of Calenberg and that this army was on its way to Bremen to liberate the city. Because the unsuccessful siege had taken months, using up the supplies, killing a quarter of his Landsknechte, and creating the danger of a mutiny, Eric decided to abandon the siege.
Deployment
Imperial troops
The imperial troops left from Bremen on 22 May, marching rapidly to attack the Protestant army. The units of the two military leaders Eric and Christoph von Wrisberg travelled along the Weser separately, one on each bank; they wanted to reunite at a river crossing. Wrisberg's troops lagged behind, however, because the sand paths caused problems. The young and ambitious duke did not wait for the latecomers and had his mercenaries march more quickly. After Eric was informed of the approach of the enemy near Drakenburg, he ordered his soldiers to get into battle formation. He had about 6,000 Landsknechte, an unknown number of horsemen, and seventeen cannons at his disposal. He positioned them east of Drakenburg towards Heemsen on an open field. He chose a corrugated terrain with sand dunes of up to in height. He regarded this as an ideal secure position to meet the enemy from. His cannons would have an open field of fire as a result of their more elevated position. Additionally, his troops had the advantage of having both the sun and the wind behind them. His troops did not, however, have any avenue for evasion or retreat, since the battlefield was bordered by swamps, wetlands, and the Weser River.
Protestants
Elector John Frederick I of Saxony had led the Protestant army shortly before his capture in the Battle of Mühlberg. Originally, the army had only consisted of several Fähnlein of Landsknechte led by. It had marched from Saxony via Nordhausen, Northeim, and Brunswick to aid the besieged city of Bremen. Troops from Brunswick, Hildesheim, Hamburg, and Magdeburg had joined the army. Thus, the army consisted of a total of 26 Fähnlein, or approximately 6,500 men, giving them a slight numeric advantage.
Battle
The Protestant troops came from the east and reached Eric's troops, who were entrenched on the dunes. The Schmalkaldic attackers availed themselves of a tactic attributed to Brun von Bothmer, a captain from Brunswick-Wolfenbüttel. He knew the area well as he lived there as a child and proposed a pincer movement with a second offensive at the Catholics' rear. Bothmer led about one thousand mounted arquebusiers to attack from the north covertly. Both parties began the battle with simultaneous shelling and assaults. In doing so, Eric's battle formation faltered. Additionally, the Protestant cavalry divided the imperial forces by riding in between the hills. In the chaos, Eric's cavalry fled, inflicting losses upon their own infantry. The Catholic forces' escape route had been cut off by the Schmalkaldic forces as well as the nearby swampland. The only escape was the Weser River, which was flooded with spring runoff. Approximately 1,000 imperial mercenaries drowned while looking for a ford. Duke Eric II swam across the river with great difficulty, but survived.
Rearguard action
The units under the command of Wrisberg reached the battlefield on 23 May, but the battle was already over. Because of their numeric inferiority they retreated towards Verden. About ten kilometers north of the battlefield, the soldiers encountered the Tross of the Protestants near Hassel. It was only protected by a few soldiers, equivalent to about one Fähnlein. The imperial forces overpowered the weak Schmalkaldic forces, seizing their war chest of about 100,000 gold guilder, which eventually they gave to Emperor Charles V.
Consequences
As a result of the Battle of Drakenberg, the Imperial army of Eric II virtually ceased to exist; Wrisberg's troops escaped to the Netherlands and disbanded. The Protestant victory contributed to the stability and freedom of religion for Lutherans and Catholics in northern Germany. The two surviving leaders, Christoph von Wrisberg and Eric II, despised each other for the rest of their lives, accusing each other of being responsible for the defeat.
