The basic rules are the same as normal OG, but the desert ground was harder, so there are a few differences:
ENTRENCHING: There is a +2 DRM towards entrenching attempts (F.1B).
GUNS: Guns may not emplace in OG (F.1A).
MOVEMENT: Vehicle movement rates are slightly different. Check the Ch. F movement chart.
Basically Open Ground which is also Concealment terrain. It does not negate FFMO/Interdiction. Also, Guns may emplace and set up HIP.
TEM: Considered open ground, with an additional -1 TEM for HE attacks vs. unarmored targets (F3.4).
IMMOBILIZATION DR: Hammada can Immobilize a non-fully-tracked vehicle. Roll each time a vehicle enters a Hammada hex, or an OG hex adjacent to a hammada hex. A DR of 12 immobilizes the vehicle, modified thusly:
+1 if in the hammada hex (as opposed to adjacent)
+1 if a large truck (>= 4 tons). Exc: British.
-1 if vehicle expends 2 times the normal MP in that hex.
Bottom line - Fully tracked vehicles are not effected. For all other vehicles, as long as you stay out of the actual Hammada hex and use 2x MP in adjacent hexes, you never have to roll for immobilization (except for big trucks). I would recommend using the 2x rate as often as possible. So this rule ends up being easy - you hardly ever use it. Also, check out the nifty Hammada Imm. chart (F3.31).
Level 0 OG with some minor exceptions:
MP: Vehicles expend 1 extra MP to exit a deir (F4.3).
LOS: Entrenched/Emplaced units in the interior of the deir (i.e... not adjacent to the edge) have LOS only one hex beyond the edge of the deir. They of course have LOS to higher levels as well, including hillocks, which are at 1/2 level. If the unit is not Entrenched/Emplaced, LOS is determined normally (F4.4).
TEM: If you are firing at a target in a deir, it gets a +1 TEM (or is HD if a vehicle) unless you are 1) adjacent to the deir, or 2) at a higher level (including a hillock) (F4.5).
This is the one everybody hates, "why couldn't they just make them gullies?" But they ARE gullies, with some minor, simple exceptions.
(And don't be fooled by F5.2 (MF/MP). It is a clarification of DEPRESSIONS in general on a hillside, not just wadis. The rules for changing levels with Depressions in play are very logical. Logic, of course, can be mind-numbing, as the recent Parker's Crossroads debate well showed. Movement on board 25 can be convoluted and complicated, and if you don't like board 25, don't play on it. I often don't. But that has nothing to do with Ch. F)
Most of the ways a wadi is different from a gully:
Both of these can also be done in reverse movement. Thus there are rear and front HD counters. Obviously, if you are IN a wadi and start to drive out forwards, use a front HD counter. Likewise, if you are outside the wadi, and start to drive in forwards, use a rear HD counter because the butt of the tank is now up against the wadi wall. Etc..., etc..
I believe the confusion here arises from the LOS rules (F6.4). But there are really only a few cases to remember. Look at the diagram below paying close attention to units A and B (assume all hillock overlays are placed at level 0):
A = on hillock X, whether Entrenched/Emplaced or not.
B = adjacent to hillock Y, non-Entrenched/Emplaced.
C = neither on nor adj. to a hillock, whether Entrenched/Emplaced or not.
D = adjacent to hillock Z, non-Entrenched/Emplaced.
Both units A and B have LOS across two full hillocks i.e... across Y and Z (for unit A don't count hillock X as one of the two) up to the first non-hillock hex past the second hillock (where unit D is above). For units A and B to see unit D, unit D must not be Entrenched/Emplaced. Other than that, units A and B can see all units, Entrenched/Emplaced or not, between themselves and unit D.
Unit C can see hillocks Y and Z, but generally not past them, with the reciprical of A and B being the exceptions.
That's it. You may think that there are other LOS paths you can trace, but there are not. The reciprocal LOS rule negates the need for any more rules. Easy, eh? Also check out the Hillock diagram in the rulebook, it's very helpful.
TEM: Unit B would get a +1 TEM (or HD if a vehicle) to fire traced through hillock Y (unless the fire originated from a higher level, of course) (F6.5).
Open Ground with a number of exceptions.
MOVEMENT: Infantry 1 + COT = 2 MF usually
Vehicles 2 (or more) + COT, see Ch.F divider for complete list
Each of the above is reduced by 1 MF/MP if the conditions are Mud or hard sand. Beaches are often hard sand, by the way (F7.3).
BOG IN/ADJACENT: The way I remember this rule is that a fully-tracked vehicle with Normal Ground Pressure bogs on a DR of 12 in a hex adjacent to a Sand hex. Adjust it from there based on the BOG DRM chart, e.g. +1 for HGP, +1 for half-tracks, etc... NOTE: Only the DRM's listed on the SAND BOG DRM chart apply! (F7.31).
TEM: Open ground, but Ordnance/OBA FP is halved (F7.4).
SAND DUNES (F7.5)
When reading the rules in the rulebook, remember that there is a difference between sand dune hexes and Dune Crest hexsides. Sand dune hexes are treated as normal sand hexes. Dune Crest hexsides are the brown hedge-looking hexsides, and are treated as a 1/2 Level obstacle, and provide a +1 TEM to fire that is not from a higher elevation. (The difference between a Dune Crest and a hedge is that you can't gain wall advantage by a Dune Crest, and a hedge often gives cover to fire from a higher elevation.)
The whole SD overlay is defined as either Low or High. Low SD are at Level 0. A SD overlay defined as High is considered entirely at Hillock level (thus, a 1/2 Level Dune Crest on top of a 1/2 Level "hillock" is a Level 1 obstacle).
Pretty much like a foxhole, with the following exceptions:
TEM: +1 to all attacks except OBA, which is +3. This is signified by +1/+3 on the counter. This is slightly different than the notation on an Entrenchment counter, since OVR is +1, not +3.
ELIMINATION: If a sangar is overrun by a fully-tracked vehicle, and the vehicle survives the overrun still mobile, the sangar is eliminated along with any Gun in the sangar. This is a pretty brutal rule, which I think discourages one from putting a Gun in a sangar. Maybe someone can think of a reason to do that, but I can't.
Also, a unit can move from inside a sangar straight under an adjacent trench counter.
This section looks like a mouthful, but it's not really that bad. The thing to remember is that you will rarely use more than one or two of any of these rules in any one scenario. So there is no need to memorize all the Desert Hindrances; I haven't. Before play read which ones are in effect (as defined by SSR), look up the given rule(s) in the rulebook and commit them to your short-term memory. I usually do a few practice dust DR to get the hang of it, and once I do that it's easy. So you can use this sheet as a reference.
The important thing to note about Desert Hindrances is that many are Low Visibility (LV) Hindrances (E3.1). Note the difference between normal Hindrances and LV Hindrances: normal Hindrances cancel FFMO and Interdiction, while LV Hindrances do not. DLV is short for Desert Low Visibility, a sub-catagory of LV Hindrances.
SUN BLINDNESS: Causes a +2 DLV Hindrance to TH and IFT DR when looking into the sun (see diagram on page F13 for the "sun CA"). Obviously if it is early morning then the sun is in the east, and if it is late afternoon the sun is in the west (F11.61).
*(Normal) Heat Haze (F11.62):
*Intense Heat Haze (F11.621):
Both levels of Heat haze cause a +1 DRM to aircrafts' Sighting TC.
Note that Light and Moderate dust are DLV's, while the more extreme dusts are LOS Hindrances, and thus negate FFMO. Also note that Light and Moderate dusts are slightly different than most LV Hindrances in that the Hindrance DRM applies to Interdiction attacks - i.e... they don't prohibit Interdiction in an Open Ground hex, but they do modify the Interdiction DR. Dust does not effect either Firelanes or Residual Firepower.
Light Dust (F11.71):
Moderate Dust (F11.72):
Heavy Dust (F11.73):
Very Heavy Dust (F11.731):
Extremely Heavy Dust (F11.732):
VEHICLE DUST (F11.74):
Placed in the hex just exited by a vehicle if it expended 2 or less MP in the hex entered. It basically follows the vehicle around until the end of it's MPh. If it is present at the end of the vehicle's MPh, it remains until the next friendly player turn. It's effects are the same as drifting dispersed smoke.
There are two types of VD counters, one for vehicles in Motion, and one for vehicles not in Motion. The only difference is that the Motion VD counter is removed in the MPh the next time the vehicle moves, and the non-Motion counter is removed at the beginning of the next friendly PFPh. Not much difference, but it can sometimes matter if you want to fire in you PFPh.
Note that VD counters do not exist in Heavy winds, thus can be removed if the wind picks up. Also, if the vehicle is wrecked, the VD counter is not removed immediately. The VD is still removed during the next friendly player turn. If a vehicle in Motion is wrecked, replace its Motion VD counter with a non-Motion VD counter (as it is no longer in Motion!).
Tactical tip: VD counters can be crucial in providing adequate cover for an advance. One technique that sometimes works well is to move tanks in Platoons of 2-3 tanks using Platoon Movement (D14). (Some may think that this is reserved for radioless AFV's, but D14.23 states that all AFV's may use this movement if they wish.) Since they are moving together, the dust from one AFV can provide cover for the other(s). It might decrease the movement rate of the platoon a little, but if that's not an issue, give it a try.
The Hindrace caused by FFE changes when dust is present. See F11.75 for a nice summation of the effects on different types of FFE's. I can't sum it up better here, so I won't.
If Dust and Heavy Winds are in effect, fire directly into the wind is subject to a +1 DLV DRM (F11.761). (Don't forget this rule in Khamsin!)
DVP: Desert Victory Points are slightly modified to reflect the increased importance of vehicles. The DVP value of vehicles are usually printed on the scenario card for easy reference (F.3)
MINEFIELDS: Minefields are not hidden in the desert, but are represented by generic minefield counters at the beginning of the scenario which hide the value of the minefield factors. Some of these markers can be "dummy" minefields, placed in order to fake out the opponent (F.7).
VEHICULAR SMOKE: Ch. F introduces a new type of vehicular Smoke grenade to ASL! Only OT or CE Closed-topped vehicles may use them. A CE vehicular crew may place a 1/2" Smoke counter in the MPh by rolling a 2 or less, and a BU OT vehicular crew can do so by rolling a 1. It is treated as a normal 1/2" Smoke counter (F.10).
REVERSE MOTION: Vehicles may now remain in motion when moving in reverse (F.11).