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Radar in Second World War at Sea
By Steve Cabral
June 2015

The development of radar was one of the defining events of World War II. In Second World War at Sea games, however, radar is virtually ignored. This optional module expands its role in the game.

Radar was first conceived in 1904 in Germany and derived by two independent designers, but the Imperial Navy felt there was no need to detect ships one couldn’t see and showed it the door. In the 1920s radar as we know it was accidentally discovered in the U.S., and the U.S., Great Britain, France and Germany all began radar development thereafter.

Radar was originally in the meter range, and during the war the U.S. and Great Britain developed centimeter wavelengths that Germany declared impossible. German naval radar fell hopelessly behind until a British centimeter set was captured. (Interestingly, the German Z-52 appears to have an American radar and director system aboard as designed, but this has not been confirmed; many German radar developments are locked away in Allied archives.)

Early Resistance

Many national and military leaders distrusted radar, and in the very traditional and conservative navies the anti-radar forces were strong. Most German and some American commanders, particularly submariners, were in constant fear that radar use could be triangulated back to them like radio. So Germans almost always kept their sets off as did many U.S. sub commanders early in the war.

The U.S. was fully radar-equipped by July 1943. During the somewhat reduced pace in operations after Guadalcanal the fleet was re-equipped with excellent electronics, and American carriers mounted as many as eight different types of sets.

The British took longer to get radar aboard ships because they were kept so busy and at sea so often, and needed to equip destroyers and escorts for the U-boat war. Some British ships like the Sheffield had surface search radar at war’s start but most got their first set when the fire control Type 284 was added in summer 1941.

The Japanese had little use for radar despite experiments starting in the 1930s. The Italians interestingly embraced radar and added Gufo (owl) sets as quick as they could, or German sets when available, and they weren’t afraid to use them. The French managed to get radar aboard three ships.

Misuse and Improvements

Early on, radar was often misunderstood and misused. Admiral Lancelot Holland, aboard Hood, ordered Prince of Wales to use Type 284 radar to search a certain arc for Bismarck while he used his to search another arc. Type 284 is gunnery-control radar and has a limited arc, unlike search radar, which usually covered 180 to 360 degrees depending on installation and nationality factors. The Prince of Wales captain signaled back — this being the Prince of Wales after all — that his radar didn’t work. Prince of Wales then requested to turn on his powerful search radar! This was denied because it would jam Hood’s T-284 radar.

In November 1942 Admiral Callaghan put together a scratch cruiser and destroyer task force to stop a massive Tokyo Express battleship fleet heading to Guadalcanal. He placed his destroyers with ineffective, early-model SC radar in the lead, his cruisers some with no radar in the center and his brand new Fletcher-class destroyers with improved microwave SG radar in the rear. The U.S. fleet was virtually wiped out, but the Fletchers, which could “see” the Japanese ships, were unscathed.

Optional Rules

The following Second World War at Sea rules cover contact by sea and air search plus radar’s use in naval gunnery. Each country’s use of radar is separate and replaces current radar bonuses for U.S. and British task forces.

French and Japanese Radar

Strasbourg received air warning radar in 1941, and Jean Bart and Richelieu received the same sets in 1942. Despite Free French upgrades, however, treat French ships as having no radar. No special radar rules apply to Japanese ships due to their excellent spotting capability.

German Radar

German radar (FuMO) was usually turned off. Roll 1D6 at the start of the scenario. If the result is a 6, each German task force with radar-equipped ships gets +1/–1 on the Contact Table.

Starting in 1942 all non-active ships use passive radar (detecting radar signals only). Whenever a task force searches for them with a modifier for radar, the German has the option to use passive detection to evade the search. If the search roll results in detection the German may re-roll the detection die; if it indicates no contact he remains unfound. If the German force is still found proceed to combat, but Germany automatically loses initiative.

Date of radar equipage in Kriegsmarine:

  • CA+: 1939
  • CL: 7/41
  • DD: 1942

British Radar

A British task force has radar whenever one of the ships listed below is included after the given date, or if it contains six or more unnamed vessels not counting CL ‘C’ class. All British task forces are radar-equipped as of 1945.

A task force is considered British if 50% or more of its ships are British, except in the Pacific. A task force is considered American if more than 50% of its ships are American, or if it’s in the Pacific.

A radar-equipped task force gets +1/–1 on the Contact Table. All gunnery combat is +1 for named ships equipped with radar.

Date of fire-control radar equipage:

  • Arethusa: 3/1/42
  • Aurora: 4/1/41
  • Belfast: 1/1/42
  • Berwick: 1/1/41
  • Birmingham: 3/1/42
  • Dido: 6/1/43
  • Edinburgh: 3/1/42
  • Enterprise: 10/1/43
  • Fiji: 12/1/41
  • Glasgow: 6/1/42
  • Hood: 3/1/41
  • Kent: 1/1/41
  • Kenya: 12/1/41
  • King George V class: all
  • Leander: 1/1/42
  • Liverpool: 12/1/41
  • London: 5/43
  • Malaya: 7/1/41
  • Manchester: 2/1/42
  • Mauritius: 2/1/42
  • Neptune: 1/1/41
  • Newfoundland: As built
  • Nigeria: 8/1/41
  • Norfolk: 9/1/41
  • Orion: 1/1/41
  • Phoebe: 4/1/42
  • Ramilles: 1/1/43
  • Renown class: 1/1/41
  • Revenge: 12/1/41
  • Royal Sovereign: 1/1/43
  • Sheffield: 6/1/41
  • Valiant: 4/1/43
  • Warspite: 1/1/41
  • Air and surface search equipage: 11/41
  • CV and DD: all
  • Air and surface search equipage: 1/45
  • All other ships.

Italian Radar

A radar-equipped task force gets +1/-1 on Contact Table. An Italian task force has radar when it includes one of the ships listed below after the given date.

Air and surface search (Gufo or FuMO): 7/42

  • Capitani Romani class: as launched
  • Legionario
  • Leone
  • Littorio
  • Maestrale
  • Pancaldo
  • Vittorio Veneto

Air search (Gufo): 8/43

  • Impero
  • Roma

U.S. Radar

A U.S. task force has radar if it includes one of the ships listed below after the given date, or if it contains six or more unnamed vessels not counting four-piper DD classes.

All U.S. task forces are radar-equipped as of July 1943.

A task force is considered American if more than 50% of its ships are U.S. or if it’s in the Pacific Ocean. A task force is considered British if 50% or more of its ships are British, except in the Pacific.

A radar-equipped task force gets +1/–1 on Contact Table only in ocean hexes. All gunnery combat is +1 from named ships after 6/43 and +2 after 6/44. The “search and fire control as built” group also get +1 prior to 7/43.

Search and fire control as of 7/43:

  • All ships

Air search only as of 1939:

  • All CV
  • California
  • Chester
  • Chicago
  • New York class
  • Northampton
  • Pensacola
  • West Virginia

Air and surface search equipage as of 7/42:

  • All DD

Search and fire control as built:

  • Baltimore class
  • Cleveland class
  • Iowa class
  • North Carolina class
  • South Dakota class

Rain Squall

Whenever an air strike arrives at a task force equipped with active radar, it is spotted on a roll 1-3 (1-4 for Allies from 1942 onward). A task force using only passive radar spots the strike on a die roll of 1.

If it spots the strike, the task force may roll one die. On a 6 it ducks into a rain squall and may not be attacked. The strike may hit another task force in the same hex if its intended target evades.

Lucky Ship Option: The U.S.S. Enterprise seemed to tow a squall wherever she went. Using this option a task force that includes her ducks into a squall on a 5 or 6. “Big E” got lucky a lot in the Pacific but the other carriers took the brunt of strikes aimed at her.

Night Radar

When used at night, radar allows a task force to detect the enemy at daytime visibility distances. Ships with gunnery radar may fire at ships that cannot be seen.

When firing at a target beyond visibility all fire must be directed at the largest target. If targets are equidistant, split the fire randomly among them. American task forces’ search radar is negated for surface detection when a battle takes place in land hexes prior to 1944. U.S. fire-control radar does work.

Radar Loss

Radar may be lost when a ship is hit by gunnery fire. For each gunnery phase hit (not per individual hit) roll one die. A result of 6 removes radar until the ship returns to port.

Unlucky Ship Option: Littorio-class BB and 1942 U.S.S. South Dakota roll not only for radar loss but also for electrical failure in each movement impulse. On a “6” the ship loses electrical power and can move only straight and can not fire. This lasts for two movement and gunnery impulses. This can only occur once per turn but carries over into an extended battle. Littorio-class ships are not affected by this in Clear weather.

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