Peter Ludwig du Moulin was the son of the Huguenot Theophil du Moulin, who, since 1681, had served in Brandenburg military. When he was 14 years old, Peter Ludwig entered as "Fahnenjunker" in the Infantry Regiment Prince Leopold von Anhalt-Dessau (Nr. 3). In 1703, he was promoted to "Fähnrich" (cadet). During the War of Spanish Succession (1701–1714), he participated in the First Battle of Höchstädt in 1703, and, subsequently, the Battle of Blenheim a year later. He was present at the battles of Cassano in 1705 and Turin in 1706. After 6 December 1707, he was promoted to staff captain, and assigned to the Prussian Crown Prince, Frederick William at the Battle of Malplaquet in 1709. Afterward, he participated in campaigns in the Great Northern War. In summer 1712 he was promoted to captain of his own company, and in December 1715, he was promoted to major of the newly-established Infantry Regiment Prince Leopold von Anhalt-Dessau (Nr. 27), in Stendal.