Magnus Julius De la Gardie was born in 1668 in Stockholm. He started his military career in the French army, where he fought for the French in the War of the Spanish Succession. After the Battle of Malplaquet in 1709, he became a Swedish Colonel at the Royal Dalarna Regiment, which he led in the Battle of Gadebusch in 1712. After the successful battle, he was appointed Swedish Major General, and in 1717 he became a Lieutenant General.