The Battle of Freiburg, also called the Three Day Battle, took place on 3, 5 and 9 August 1644 as part of the Thirty Years' War. It took place between the French, consisting of a 20,000 men army, under the command of Louis II de Bourbon, Duc d'Enghien, and Henri de La Tour d'Auvergne, Viscount de Turenne, and a Bavarian-Imperial army of 16,800 men under Field Marshal Franz von Mercy. On 3 and 5 August, the French suffered heavy casualties despite having greater numbers. On the 9th, Turenne's army tried to flank the Bavarians by heading to Glottertal through Betzenhausen and cut off their supplies, while Mercy moved to St. Peter where they faced off against each other. The Bavarians repelled the attack of the French vanguard and retreated while leaving behind parts of their baggage and artillery. Having resulted in heavy casualties on both sides, the French side claimed victory because of the Bavarian retreat but the battle is also often seen as a draw or a Bavarian tactical victory as the French army took much heavier casualties and failed their goal of relieving or retaking Freiburg. However, France gained a strategical advantage in the following campaign by leaving Freiburg behing and reaching the sparsely defended Upper Rhine region prior to Mercy and in consequence conquering large parts of it.
The confontation between France and Bavaria continued, leading to the subsequent battles of Herbsthausen and Nördlingen in 1645. This series of battles lasting since Tuttlingen 1643 signalled the nearing of the end of the Thirty Years' War. The huge losses suffered in Freiburg weakened both sides and were a huge factor that led to the Battle at Nördlingen, where Von Mercy was killed. The successors of Mercy were not as adept and efficient as he was, which led to Bavaria suffering multiple invasions in the following years. Maximilian, in the wake of the devastating invasion of 1646 temporarily withdrew from the war in the Truce of Ulm 1647.