There are a number of skills spread throughout the Call of Cthulhu and Delta Green books, and many fill the same role or are contradictory. The skill set used on this website reflects a Keeper owning the Call of Cthulhu, 5.5 edition, the Delta Green sourcebook, and the DG: Countdown sourcebook. To this skill set have been added a number of skills from the Keeper's Companion, Vol. 1, as well as new skills.


Forgery (01%)
(p.281, Delta Green)
The skill follows the given description except for the following. A failed Forgery roll means that the documents are flawed in some respect. A successful Spot Hidden roll will detect this flaw. Due to this, it is important that the characters do not know what the Forgery roll was when it is made.

Heavy Weapon (05%)
(p.189, Keeper's Companion vol 1)
This skill is used when operating all manner of crew-served weapons, including mortars, artillery, naval guns, and tank guns, with the exception of crew-served machine guns (use the Machine Gun skill). The Heavy Weapon skill, used with the Navigate (Land) skill, is also used to call in artillery or an airstrike on a target through the use of radio communications or signals.

Pilot Boat (01%)
(p.67, Call of Cthulhu, 5.5 edition)
The Pilot Boat skill is solely for the operation of small motor craft, ranging from a rowboat with an outboard motor up to a fishing vessel, landing craft, or PT boat. The Boating skill (described on p.280 of the Delta Green sourcebook) is used when operating non-motorized vessels like kayaks or rubber boats, while the Sailing skill (described on p.281 of the Delta Green sourcebook) is used when operating sail-powered craft. To steer larger surface vessels from destroyers to battleships requires the Pilot Ship skill.

Surgery (01%)
(p.283, Delta Green)
This skill is the same as written, but is expanded upon by the following. Basic surgical tools are required to perform the skill, though ad-hoc tools can be used instead. A sterile environment with proper medical equipment like oxygen and anathesia provide the best conditions, but they are not necessary. Surgical treatment can only be performed once per game hour. The roll is modified by the following:

For every other surgeon* involved +10% up to +20%
For every nurse* involved +5% up to +20%
Complete field conditions (no anesthesia, proper surgical tools, oxygen, or sterile enviroment) -30%
WWII field hospital conditions (MASH environment) -15%
Surgical room conditions (fully-equipped surgical room) +0%

*A surgeon is defined as anyone with a Surgery skill of 60% or more. A nurse is defined as anyone with a Medicine skill of 30% or more.

To perform surgical treatment on a patient, follow this procedure:

  1. Roll against the modified Surgery skill.
  2. Success raises the character's HP by 1D10 to no more than 1 HP. Surgical treatment cannot restore lost HP, but simply raises a character's HP above zero.
  3. Failure means that the character loses 1D4 HP and the character will die in the following round unless they are stabilized by a successful First Aid or Medicine roll. If the character's HP drops below -30, then they are immediately dead on the operating table.

Survival (10%)
(p.247, Delta Green: Countdown)
This skill is as defined in Countdown, except that characters must specify which environment the survival skills are for. These environments can include the following: The Desert and Polar Survival skills are required to operate effectively in those environments, as they are the most hostile on Earth. Characters with 60% or more in any Survival skill does not have to roll except in the most extreme situations, such as blizzards or sandstorms.

Swim (25%)
(p.201-2, Keeper's Companion vol 1)
According to the description in the Keeper's Companion, those with the Swim skill of 60% or more are experienced with snorkeling and understand water conditions, safety, and depth procedures. These techniques are of great importance to combat divers during the Second World War, as SCUBA would not become available until after the war. Divers with a CON and DEX of 10 or more and a Swim skill of at least 60% can perform high dives (diving from a height of up to the Swim skill in feet with a successful Swim roll or 1D6 damage) and free dives (diving to a depth of the Swim skill in yards on a successful Swim roll or lose 4D6 in CON, which can cause the character to begin drowning).


Aerial Gunnery (15%)
This skill is used when either firing fixed weapons as on a fighter aircraft or dropping bombs. The Machine Gun skill is used when operating flexible-mounted machine guns on bombers.

Drive Bicycle (20%)
This skill is used when operating a non-motor-powered bicycle at high speed (30 MOVE or more), through difficult maneuvers, or under adverse conditions, all of which require a skill check. Failing a skill check results in 1D4 damage for every 10 MOVE above 10 the cyclist is traveling.
      The maximum speed (in MOVE) of a bicycle is determined by the STR of the cyclist. A cyclist can pedal STRx1 in MOVE per round (STRx2 on an incline) only requiring a CONx5 check every hour, or they may exert themselves to pedal STRx3 in MOVE per round (STRx4 on an incline) requiring a CONx5 check every round. Those with over 60% skill in Drive Bicycle can exert themselves (STRx3 MOVE/round) requiring a CONx5 check every minute instead of every round.

Navigation (Desert) (00%)
The ability to navigate in the featureless wastes of the desert by using a sun compass, vehicle speedometer and map. The navigator takes a bearing on a distant object, keeping the sun's shadow form the compass's spike on a pointer. A sun compass gives a true instead of magnetic bearing. The user must know the basics of navigation (Navigation (Land) must be 25% or better), and uses the Astronomy skill at night to confirm their position.

Pilot Glider (01%)
Gliders were in strong use by many of the combatants of the Second World War. Gliderborne infantry was a mainstay of airborne forces in the British, German, and American armies, and special operations troops often used gliders for insertion, including the raid on Eben Emael and Skorzeny's rescue of Mussolini. The Pilot Glider skill is for the operation of these assault gliders. Those with Pilot Aircraft skill can use that skill instead of Pilot Glider.

Sabotage (05%)
The knowledge and techniques required to sabotage equipment and vehicles with or without explosives. A successful Sabotage roll will aid a Demolitions skill check. A successful Sabotage roll will indicate that user knows how to disable the equipment or vehicle without explosives. A successful Sabotage roll disables the target for 1 or 2 days. A critical Sabotage roll means that the target has been disabled for weeks, months or permanently depending on the nature of the target.

Shiphandling (01%)
Shiphandlers know how to run a ship or boat, making the most efficient use of craft and crew. The skill is usable only by the commander, and is rolled only when the gamemaster calls for it. If you want to get the best sailing speed or row most efficiently or take proper advantage of the tides, your Shiphandling skill can help. Differentiate it generally from Boating by recognising that Shiphandling is concerned with the strategies and tactics for conduct in fresh and salt water. Differentiate it from the Sailing skill by recognising that Sailing only concerns the techniques of handling vessels with sails. The Shiphandling skill will always take precedence over either Boating or Sailing, and is a true command-level skill.

Skiing (01%)
This is the skill of using snow skis for either downhill racing or, more likely for WWII operations, for cross-country movement. Ski training was often given to some units of mountain divisions and special troops like the Devil's Brigade and the Norwegian commandoes who struck the German heavy-water plant supplying their atomic bomb effort. A skill check is required whenever skiing down any but the lowest of slopes, and failure results in 1D4 damage for every 10 MOVE above 10 the character was skiing (ie. a character skiing at 32 MOVE can suffer 2D4 damage on a failed skill check). Those with 40% or more in Skiing only have to roll when negotiating steep slopes, are skiing at high speed (25 MOV or more), are attempting to outmaneuver a pursuer during a chase (see below), or are firing a weapon while skiing.
      A character can ski at a MOVE of STRx2 per round while skiing cross-country over low slopes, and at a MOVE of STRx3 per round while speeding down steep slopes. Skiing at these speeds requires a CONx5 check every hour, with failure requiring the skier to stop and rest for 1D10+20 minutes. Skiers can exert themselves to greater speeds of a MOVE of STRx3 per round cross-country and MOVE of STRx5 per round downhill by rolling a CONx5 check every round, with failure requiring the skier stop and rest for 1D10+20 minutes. Chases between skiiers use the rules for chases on foot.