As the U.S. military grew in size following the American Civil War, joint military action between the Army and Navy became increasingly difficult. The Army and Navy were unsupportive of each other at either the planning or operational level and were constrained by disagreements during the Spanish–American War in the Caribbean campaigns. The Joint Army and Navy Board was established in 1903 by President Theodore Roosevelt, comprising representatives from the military heads and chief planners of both the Navy's General Board and the Army's General Staff. The Joint Board acting as an "advisory committee" was created to plan joint operations and resolve problems of common rivalry between the two services.