On September 3, 1939, the British and French declarations of war on Germany initiated the Battle of the Atlantic. The United States Navy Chief of Naval Operations (CNO) established a combined air and ship patrol of the United States Atlantic coast, including the Caribbean Sea, on September 4. President Franklin D. Roosevelt declared the United States' neutrality on September 5, and declared the naval patrol a Neutrality Patrol. Despite the name, the Neutrality Patrol greatly favored the British, because the Royal Navy had significantly greater access to the Atlantic.
On September 4, 1939, the CNO ordered the Atlantic Squadron to establish a combined air and ship patrol to observe and report the movements of warships of warring nations within a line extending east from Boston to 65 degrees west and thence south to the 19th parallel and seaward around the Leeward and Windward Islands. The concept of a naval Neutrality Patrol within that zone was presented to a Conference of Foreign Ministers of the American Republics convened in Panama on September 25. After considerable debate, the conference agreed on October 2, 1939, to extend the neutrality zone southwesterly parallel to the northeastern coast of South America approximately 300 miles (480 km) offshore.
Battleships USS Arkansas, Texas and New York with the aircraft carrier USS Ranger (with aircraft squadrons VB 4, VF 4, VS 41 and VS 42 embarked) formed a reserve force at Hampton Roads to support the following patrols:
- Patrol Zero: Destroyer division 18 of USS Davis, Jouett, Benham and Ellet were assigned patrol station zero from Newfoundland south to the 40th parallel.
- Patrol One: Destroyers USS Hamilton and Leary were assigned patrol station one along a northwest-southeast line off Georges Bank.
- Patrol Two: Destroyers USS Hopkins and Goff with aircraft of patrol squadron 54 and seaplane tender USS Owl operated from Newport, Rhode Island, between the 38th and 43rd parallels.
- Patrol Three: Destroyers USS Manley, Barry, Decatur and Reuben James patrolled between the 34th and 38th parallels with aircraft of patrol squadrons 52 and 53.
- Patrol Six: Destroyers USS Babbitt and Claxton patrolled the Florida Strait and Yucatan Channel.
- Patrols Seven and Eight: Cruisers USS San Francisco and Tuscaloosa with destroyers USS Broome, Borie, Simpson and Truxton patrolled the eastern Caribbean Sea south of the 23rd parallel with aircraft of patrol squadrons 33 and 51 supported by seaplane tenders USS Lapwing, Gannet and Thrush. Gannet and Thrush established a seaplane base in Puerto Rico.
- Patrol Nine: Cruisers USS Quincy and Vincennes patrolled within 300 miles (480 km) of the coast between Newport and Cape Hatteras.
The CNO orders of September 4 directed the patrols to report the movements of warships of warring nations in cipher. U.S. Navy ships were initially instructed to avoid making any report while in the vicinity of such warships to avoid performance of unneutral radio direction finding service or the impression that an unneutral service was being performed. On October 9, President Roosevelt instructed the navy to promptly transmit reports in plain English; and the Neutrality Patrol was instructed on October 20 to report contacts with plain-language radio transmissions.
The Royal Navy destroyer HMS Hyperion intercepted the German liner Columbus on December 19 after three days of radioed position reports by Neutrality Patrol destroyers and cruisers. The Neutrality Patrol similarly radioed position reports of the British RFA tanker Patella a few days later, but there were no German ships in position to intercept. The German freighter Konsul Horn left Aruba on January 7, 1940, posing as a Soviet ship to avoid identification by the Neutrality Patrol. The German freighter Helgoland sailed from Colombia on October 24, 1940, and evaded pursuit attempts by Neutrality Patrol destroyers. The German freighter Rio Grande similarly evaded the Neutrality Patrol by sailing from Rio de Janeiro on October 31; but USS Plunkett prevented German ships Orinoco and Phrygia from leaving Tampico, Mexico on November 15.
Neutrality Patrols began operating from Bermuda following the Destroyers for Bases Agreement. The base was commissioned on April 7, 1941; and Carrier Division 3 (USS Ranger, Wasp, and Yorktown) began using the base the following day. By mid-June cruisers USS Memphis, Milwaukee, Cincinnati and Omaha were patrolling from Trinidad south along the coast of Brazil.
In early 1941, President Roosevelt secretly organized a protection-of-shipping task force 24, given the designation of Support Force, United States Atlantic Fleet, under the command of Rear Admiral Arthur L. Bristol. Ships, planes, funding, and personnel were assigned in January and February, and operations began in March. Admiral Bristol remained in Washington, but material for the various bases was assembled and shipped from Naval Air Station Quonset Point. Admiral Bristol insisted that all records be destroyed when an operation was completed. His staff believed he was following Presidential instructions to avoid revealing operations which might not have public-opinion approval. Efforts to document Support Force operations after the war were discouraged to avoid damaging world opinion as to the integrity of United States neutrality.
To augment the fleet units already engaged in the Neutrality Patrol which President Roosevelt had placed around the eastern seaboard and Gulf ports, the United States Navy recommissioned 77 destroyers and light minelayers which had lain in reserve at either Philadelphia or San Diego. In Newfoundland on August 9, 1941, President Roosevelt agreed to provide American destroyers as escorts for the Canada to Iceland portion of HX convoys and westbound ON convoys. USS Greer ineffectively engaged U-652 on September 4; and on September 11 President Roosevelt declared Axis ships entered the neutrality zone at their own risk, and ordered the U.S. Navy to attack any vessel threatening ships under American escort. HX 150 sailed September 16, 1941, as the first convoy with American escort. ON 18 sailed September 24 as the first westbound convoy with American escort. The Gleaves-class destroyer Kearny was torpedoed while escorting Convoy SC 48 on October 17, 1941. Reuben James was torpedoed and sunk on October 31, 1941, while escorting Convoy HX 156.
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- "Strict Neutrality - Britain and France at War with Germany: September 1939 - May 1940". United States Navy and World War II. Naval-History.net. Archived from the original on 2006-11-18. Retrieved 2007-05-14.
- Capt. William E. Scarborough, USN (Ret.). "The Neutrality Patrol: To Keep Us Out of World War II? Part 1" (PDF). Naval Historical Center, United States Navy. Retrieved 2007-05-14.
- Capt. William E. Scarborough, USN (Ret.). "The Neutrality Patrol: To Keep Us Out of World War II? Part 2" (PDF). Naval Historical Center, United States Navy. Retrieved 2007-05-14.
- Cressman, p. 2
- Potter & Nimitz, p. 548
- Morison, pp.14&15
- Cressman, p.5
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- Cressman, p.3
- Cressman, pp.8&9
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- Morison, p.83
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- van der Vat, p.205
- Cressman, p.50&51
- Morison, p.86
- Morison, p.90
- Morison, p.93
- Morison, p.94