I) Stealth and Observation rules
 

Stealth and observation are opposite partners in the act of surprise and ambush. These skills are unlike any other in that every person has at least some skill (Skill value 0, asset based on agl and int). Those who train in these skills will become experts in sneaking up to the enemy unnoticed, and laying ambushes (stealth), or spotting such ambushes before they are sprung (observation). Since most of the warfare in the games these rules depict (Twilight 2000, Traveller New Era, Dark conspiracy) depend on ambush, undetected movement, and small units, then these skills are of paramount importance. Unfortunately there is no clearly defined way in which these two skills interact, so a possibility is presented here.
 

Contested skill
 

The basic die roll is made for both observation and stealth for both the target as well as the ambusher. This technique is best used when both PC's involved are of major importance as 4 die rolls are used for each movement phase. The basic difficulty for the observation skill roll depends on effective range band, which will be altered depending on environmental variables.
 

Range:	Close	Short	Medium	Long	Extreme
Difficulty:	Easy	Average	Difficult	Formidable	Impossible

 

The basic roll for stealth is always Average, modified by circumstances.
 

Die rolls are made at the moment the PC's enter each other's extreme range band. No new die roll is made until; a/ a new variable is added (such as firing a starshell, or lighting a cigarette),b/ PC status changes via orders or events (such as a diversionary attack forcing troops to alert status), c/ Communications are received from another player (radio warning from forward observer), or d/ a new range band is entered by movement.

Results are determined by success level.
 

Stealth / OBS->	Crit Failure	Failure	Success	Crit Success
Crit Failure (n+10)	Contested	Spotted	Spotted Init.	Spotted Init.
Failure	Not spotted	Contested	Spotted	Spotted Init
Success	Free move	Not spotted	Contested	Spotted
Crit Success (n-10)	2 free moves	Free move	Not spotted	Contested

 

Contested= Success (spotted/not spotted) is determined by the difference between roll needed and roll made. In the event of a tie, success goes to whoever had the easier task. In any case, a contested result means that the observer has some inclination that something is out there, and can change status if desired.

Spotted= The observer has spotted the sneak. To determine distance, roll d10/10* the difference in range band (i.e. short:20, medium:40, difference=20) and add the closer range band (i.e. a roll of 5, times the difference (20) is added to the short range (20) has a distance of 30 meters).

Not spotted= the PC's remain unspotted until one of the above conditions are met (Page 2).

Spotted, Init= The observer has spotted the ambush at the maximum distance for that range band.

Not spotted, Free move= The sneak can close past the next range band without being noticed, if that is the immediate next move. (2 free moves follows the same rules, the observer is so careless, and the sneak so stealthy, that if the sneak spends the next turns closing the distance, these moves are free of die rolls, and the sneak remains unseen).

Close Range Rule:
The free move rule and close range bands mean that a PC can literally walk up to within a few inches of another without being spotted. This represents surprise only (sneaking up to someone when their head is turned), unless the target is asleep, the sneak gets only 1 action before another die roll is made for detection.

Some sample ranges are given below, others will have to be estimated based on these values (ranges in meters)
 

Environment or special circumstances	C	S	M	L	E
Open plain, full daylight	50	200	500	1000	2000
As above, but target prone	25	100	250	500	1000
Open plain, night	12	50	125	250	500
Light Forest, Daylight	10	20	40	80	160
Light forest, Night	5	10	20	40	80
Heavy forest/jungle daylight	5	10	20	40	80
City, daylight	5	10	40	200	500
City, Night	5	10	20	100	200

Note that for cities, there are plenty of opportunities to sneak very close to an enemy position (thus low Close/Short ranges), but PC's could be spotted quite far away if a keen eye spots them down a roadway. Nightfall generally cuts visibility in half (assuming a starlit night), or by 1/4 if overcast. Rain and snowfall reduce visibility to ½ and 1/3 in addition (mostly due to the loss of hearing). Night vision equipment or illumination starshells will make regions within their radius equivalent to daylight. Binoculars will double long and extreme ranges, but do not help shorter ones. A telescope will help (tripling range) only if the target is known (such as observing a base or outpost).
 

In addition, several factors will modify the difficulty of the die rolls.
 

Factor	Modifies	Difficulty
Proper camaflauge equipment	Obs	+1
Nearly asleep	Obs	+2
At Ease	Obs	+1
Lots of cover	Ste	-1
Complete lack of cover	Ste	+1

Addendum from Matt

If you want to get into party size modifers, it would depend a lot on deployment. Maybe take two basic examples, line abreast doing a sweep, or single column with a point man. In a sweep, you are trying to flush out hidden enemies, so detecting the soldiers conducting a sweep is probably 1 level easier (*2 probability) to observe a platoon (20-40 men) doing a sweep, and maybe +3 to observation to observe a squad (3-5 men) doing a sweep. The soldiers conducting the sweep will also have an easier time spotting hidden enemies, take the average observation (combine best and worst to save time), but you get to roll twice. [rationale is that working in a group sweep is more difficult than being on your own in terms of spotting things if you teammates are inobservent fools, but if there are many pairs of trained eyes they will spot things fast. In a sweep, every point is covered by at least two fields of view, so two rolls] In a single file column with a point man at least 5-10m ahead of the line, the tactics are to minimize noise during travel. So the observation bonus to spot a column of men would be something like +3 for a platoon, and +1 for a squad. Observation by the column of men would depend entirely on the point man, who would recieve no bonuses or penalties for the men trailing behind him. Some interesting combinations occur. Sweep vs Sweep- they would spot each other early at longer range. This would probably result in both sides taking cover and spending all afternoon taking pot shots at each other or trying to flank or sneak closer in smaller groups or individually. Column vs Sweep- really bad for the column if they get caught, lots of enfilade fire, and a potential for envelopement. If you get caught like this, the tactic is to scatter to the sides and back up into a line parallel to the enemy. Column vs Column, they will likely meet at closer ranges and it can turn into a real intense fast firefight as both sides deploy hastily. Or there is a good chance they can march right past each other and never know it. Of course you could have a third "no tactical consideration" option like a column without a point man (which most travelling people tend to string out into, with uneven spacing, bunches and gaps), or a mob formation. In the pointless column I would give the same observation bonus as above to spot them, but assign a -3 to *1/2 penalty for whoever happens to be at the front of the column to spot enemies (depending on distance from the rest), and a *1/2 or worse penalty for the mob to spot anything, but two dice rolls. Spotting a mob of 3-5 is +3 easier, and a mob of platoon sized is *2 or *4 easier depending on how rowdy they are. Drunken mobs cannot spot beyond short range.