He spent most of the next decade serving in the Dutch States Army, then considered the best place to learn the 'art of war' due to its success in the Eighty Years War against Spain. Many officers who later fought on both sides during the Wars of the Three Kingdoms did the same, among them Sir Thomas Fairfax and Sir Philip Skippon. During the Capture of Maastricht in 1632, he served in a regiment commanded by the Earl of Oxford, who was killed in the final assault and replaced by George Goring. By 1637, Monck was Lieutenant Colonel under Goring and played a decisive role in storming Breda, a Dutch success which was one of the last major actions of the war. After quarrelling with the civil authorities of Dordrecht, he surrendered his commission and returned to England in 1638.