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25) War Diary of the Eastern Sea Frontier
Dec 1941- Sept 1943

(Selected Excerpts Pertaining to the Defenses of the Southern New York Harbor)
Updated: October 23, 2000 (HTML code changes)

Poor pre-war defensive planning, not "a careless word"
led to the sinking of many ships by a few German
submarines just offshore America's Eastern Sea Frontier.
(Source: National Archives and Records Agency)

The Army and the Navy developed sophisticated anti-submarine detection systems to combat the German U-Boats that were attacking shipping close to the shore and inside America's harbors on the East coast from January of 1941 to July of 1942.

The Army maintained many fire control base end stations that were used as lookout posts. Patrol planes of the Navy (as well as Navy blimps), Army, Coast Guard, and the volunteers of the Civil Air Patrol were assisted by sightings from Pan Am Clippers and other airliners spotting submarines, sinking ships, oil slicks, or liferafts. Coast Guard Stations and ships, as well as fishing and merchant vessels, also made similar reports.

Magnetic detection loops were laid along the bottom of the New York Harbor in the Ambrose Channel to detect submarines that could not be detected by the newly developed radar system. The SCR-582 harbor surveillance radar was used to detect targets at night and in poor visiblity conditions. The SCR-296 fire control radar was used to determine precise bearings and ranges for gun batteries. B-17 aircraft from Mitchel Field were equipped with radar sensitive to detect the periscope of a partially submerged U-Boat. Other aircraft were equipped with MAD (Magnetic Anomaly Detection) equipment that not only detected submarines, but often detected the wrecks of ships that were previously sunk by German submarines.

Radio Direction Finding (RDF) sets were used by the Army, Navy, Coast Guard, and the FCC to triangulate on the Enigma encrypted radio signals sent by the German U-Boats. RDF stations were established at Jones Beach, LI, Sea Isle City, NJ, Montauk, LI, as well as other locations along the shore. These RDF stations (and other radio stations) not only intercepted German radio traffic, but also the SSS signals (send help, ship torpedoed) from ships that had become the victims of the U-Boats.

Underwater listening equipment called "hydrophones" were connected to shore based stations. They were also dropped from blimps and ships to listen for submarines. Sonobouys were later installed to act as remote listen stations. The type JN-1 sound ranging equipment was later used by ships to determine the distance to the targets detected.

Contact minefields were laid in the New York Harbor. These minefields were set to the "contact mode" when a loop or hydrophone detected a possible submarine. The mines would then indicate to Army personnel stationed in a Mine Casemate bunker when they were struck by a ship. The mines could then be detonated by the Mine Casemate to destroy the enemy ship.

When a loop or hydrophone detected a possible enemy submarine in the harbor, a submarine net located at the Narrows between Fort Wadsworth in Staten Island and Fort Hamilton in Brooklyn was closed. A net tender vessel was stationed at this normally open net, and closed the net upon orders from the Harbor Entrance Control Post (HECP).

In addition to the US Army using mines, German submarines laid mines in the New York, and other American harbors. Minesweepers would routinely conduct mine sweeping operations to keep these harbors safe for friendly traffic.

All of this information was collected and plotted on a daily basis, by Naval Personnel of the Eastern Sea Frontier Command at 90 Church Street in Lower Manhattan. The Army and Navy jointly operated the Harbor Entrance Control Posts (HECPs) at all protected harbors.
The Eastern Sea Frontier Headquarters at 90 Church Street

The harbor defenses of Southern New York were controlled by one HECP at Fort Wadsworth in Sataten Island, NY, an Advance HECP 1 at Fort Hancock at Sandy Hook, NJ, and an Advance HECP 2 at Fort Tilden in Rockaway, NY. Click here for more details about Fort Tilden's HECP

The following excerpts pertaining to the defenses of the Southern New York Harbor were derived from the "War Diary" of the Eastern Sea Frontier from Dec 1941- Sept 1943. This document is available on 7 reels of microfilm at the Naval Historic Research Center, Washington Navy Yard (Item reference NRS 1971-48)
1/31/41 -- At NAS NY, Floyd Bennett Field, twelve OS2U-3 and three J2F-5 patrol aircraft were each equipped with 2 MK-XVII depth bombs.

2/14/42 to 2/21/42 -- Anti-aircraft gun training will be conducted at Fort Tilden between 100 and 130 degrees true, out to 20,000 yards.

3/4/42 -- A submarine was sighted 1.5 miles offshore at Beach 97the Street in Rockaway heading westbound. Seven patrol vessals responded to patrol the area with negative results.

3/31/42 -- At Mitchel Field on Long Island, the US Army had the following aircraft available for maritime patrol, three B-18 and four B-25 bombers.

4/11/42 -- Squadron VS1D3 at NAS NY, Floyd Bennett Field, had eighteen OS2U-3 aircraft, and the Coast Guard had nine OS2U-3 aircraft available for patrol.

5/1/42 -- A Navy plane from NAS NY, Floyd Bennett Field attacked a periscope off Fire Island, Long Island.

5/17/42 -- A type 122 electric mine washed ashore at West 57th Street in Coney Island, Brooklyn and was recovered by the police.

5/21/42 -- 0430 Hours, HECP (Harbor Entrance Control Post) reported a signature on loop 2B (Rockaway and Ambrose). Craft identified as on surface. Being investigated by Navy.

6/1/42 -- Police informed ComThree that a metal cylinder, possibly a mine, had been found on the beach at Rockaway Point, L.I.

7/14/42 -- "2030 Hours, Policeman and Army observer reported sighting sub one mile off Rockaway Beach, L.I. Several boats were sent to investiagte and found nothing. PC-64 was in area and might have been mistaken for a sub. Water is shallow for some distance off shore with depth about 30 feet at one mile off." (Note: PC is a Navy designation for a minor war vessel used as a Submarine Chaser)

8/25/42 -- "2115 Hours, Radio Operator, H.E.C.P. Fort Wadsworth reported having heard unidentified vessel calling CORA, (the call for any naval aircraft at scene of action). Vessel reported it had contact or was attacking 080 degrees True, 43 miles from Cholera Bank. Position is about 40 35N; 72 30W. Unable to obtain further information"

9/26/42 -- CGR-4331 reported a floating mine 1/2 mile off Rockaway Inlet, NY. (CGR is the designation for a type of Coast Guard Vessel)

10/13/42 -- Unidentified signal on loop in vicinity of Ambrose, not on radar. Position 1 and 3/4 miles NW of Ambrose.

10/23/42 -- EDC reported contact on loop 2B. Nothing found.

10/29/42 -- CGR reported wake 40 33N; 73 46W, 2 miles South of East Rockaway breakwater.

11/13/42 -- "1117 Hours, YMS-20 witnessed inder water explosion two miles from Ambrose in 40-25-42N; 73-44-00W, bearing 170 degrees True from minesweeper, range 300 yards. YNS-20 considers explosion actuated by reverse pulse. Column of water 200 feet high was seen. EDC reports all Army mines have been accounted for. Explosion evaluated as magnetic mine or old depth charge. Port entrance closed until 1800/14 while twelve minesweepers operate in area".

11/8/42 -- HECP Wadsworth reports vessel CARETTA collided with net at gate.

11/17/42 -- 0844 Hours, Unidentified medium sized vessel signal on loop 2B. Also at 1103 Hours, a medium sized vessel outbound, at 1111 Hours a medium sized vessel outbound, and at 1116 Hours a medium sized vessel inbound. Visiblity poor.

11/24/42 -- 1448 Hours, Unidentified medium sized vessel signal on loop 2B. Possibly one of 3 minesweepers in area. At 2109 Hours, an unidentified small sized vessel signal on loop 2B in Ambrose. Radar cannot classify. HECP reports target is outbound at 4 knots. CG 83342 was sent out and nothing was found.

11/25/42 -- An unidentified small sized vessel signal on loop 2B in Ambrose. Radar unable to identify.

11/27/42 -- CGC 494 reports strong contact off Ambrose and then lost.

11/30/42 -- "0439 Hours, EDC received report from HECP NY that between 0439 and 0511 five unidentified vessals were coming in over loops 2A and 2B. Gate immediately alerted to close. Position of vessels: Azimuth 175 S 19,000 yards. Range from Water Witch radar station. At 0625 gate was ordered closed. Harbor defenses alerted. Blimp and 5 SC ordered to search. Gate was reopened at 0800."

12/2/42 -- Unidentified signal on loop 2B at Sandy Hook.

12/5/42 -- Unidentified small signal on loop 2A, no radar contact.

1/17/43 -- HECP NY reported Sonobouy 14 and 16 recorded small signature at 2230 and 2231. Gate closed 2318 until it was reopened at 0207.

1/29/43 -- Mines wash ashore at Monmouth Beach and Asbury Park.

2/27/43 -- HECP NY reported that CG 38477 (38 foot) ran into gate obstruction north of YNg3 (Gate Tender). She was abandoned and sunk in 30 feet of water.

3/29/43 -- Explosion onboard ESSO MANHATTAN, unknown causes. Port closed, later reopened on 3/30/43 at 0915. Explosion was determined to be from onboard and not caused by mine ortorpedo.

4/1/43 -- The following aircraft were stationed at Floyd Bennett Field in Brooklyn (NAS NY): Squadron VS34 with eighteen OS2U-3, and one J4F-2. Squadron EAD with one JRF and one J2F-5, Coast Guard with three J4F-1 and one PH. At Mitchel Field the Army had seven B-18-R and four B-24 bomber aircraft.

4/20/43 -- PC-1169 reported floating mine in Chapel Hill Channel (North of Sandy Hook). Recovered and identified as an Army mine. Three more mines washed ashore between Sandy Hook and Belmar, NJ. A fourth, additional mine was found 1/2 mile off shore inside of Sandy Hook,NJ.

8/1/43 -- The following aircraft were stationed at Floyd Bennett Field: Squadron VS34 with eighteen OS2U-3, one J4F-2, and two So3C-2, Squadron VB128 with twelve PV-1, EAD with 1 JRF-5, and the Coast Guard with one PH-3, three J4F-1, one JRF, and six S03C.

8/7/43 -- PV-1 (P-9 of VB128) from Floyd Bennett Field, Brooklyn found and attacked an enemy sub. The plane was shot down by the sub within 15 miles of 37-35N; 71-20W. The crew of two was wounded and picked up by a PBM aircraft. At NAS Lakehurst, there were eleven type ZNP blimps, and at Mitchel Field in Long Island, the Army had nine B-17 and one B-34 aircraft.

8/19/43 -- What was believed to be an Army mine was recovered in Rockaway Inlet by CG-83345.

9/26/43 -- An OS2U aircraft from Floyd Bennett Field crashed 7 miles S of Little Egg Inlet (Near Atlantic City, NJ). Two survivors were picked up by CG 83340.

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