Smith served in the Navy during the period of the Commonwealth, commanding ships at several of the battles of the First Anglo-Dutch War. He continued in the Navy after the restoration of the monarchy and was involved in further actions with the Dutch, during the Second Anglo-Dutch War. He rose through the ranks to become one of the junior commanders of the royal fleets, and at times commanded squadrons of his own on independent cruises. He was heavily involved in the St. James's Day Battle, where he commanded the English rear, and fought a hard-pitched battle against a Dutch squadron under Cornelis Tromp. Smith became involved in a professional rivalry with another naval officer, Sir Robert Holmes, but successfully repudiated charges of cowardice, and held office in the naval administration, until his death in 1675.