Viertageschlacht
At the start of the Second Anglo-Dutch War (1665–67), Rupert was appointed as one of the three squadron commanders of the English fleet, under the overall command of the Duke of York, taking as his flagship. As the commander of the White Squadron, Rupert fought at the Battle of Lowestoft in 1665, breaking through the enemy defences at a critical moment; Rupert's leg was injured in the battle, an injury that caused him ongoing pain. Recalled to accompany the King during the plague that was sweeping London, Rupert continued to argue in favour of the fleet's seeking a set-piece engagement with the Dutch that would force the Dutch back to the negotiating table. The following year, Rupert was made joint commander of the fleet with Monck and given the opportunity to put this plan into practice. In June 1666, they fought the Dutch at the Four Days' Battle, one of the longest naval battles in history; the battle saw the new aggressive tactics of Rupert and Monck applied, resulting in "a sight unique till then in sailing-ship warfare, the English beating upwind and breaking the enemy's line from leeward." However, the Four Days' Battle was considered a victory for the Dutch, but the St. James's Day Battle the following month allowed Rupert and Monck to use the same tactics to inflict heavy damage on the Dutch and the battle resulted in a significant English victory. The Dutch however would see a favourable end to the war with the decisive Raid on the Medway.