My recent encounter at Tanigawa's Outpost resulted in an overwhelming victory for the Imperial Japanese defenders, so much so that their caves were never even approached by the defilers of the Empire. Nevertheless, preparing for the scenario prompted me to review my cave-busting tactics. One tactic that has always fascinated me is WP grenade placement into the cave, and I wondered how effective it is. Should units with six or seven FP, especially if they are ADJACENT, Prep Fire, or could tossing WP grenades be more effective? I decided to find out by computing some rough and ready statistics.

The procedure for placing WP grenades into a cave requires two drs. First, you have to pass the normal smoke grenade dr [A24.1] (with the +1 drm for WP), then you have to make a dr to see whether the grenades land in the cave (1-3) or in the entrance hex (4-6). If the WP grenades land in the cave, however, the payoff is big: the defender has to take the usual WP NMC, but WP placed in a cave is an automatic critical hit [G11.85] (there is no NMC if the WP grenades land in the thrower's Location; otherwise their use would be rather risky).

An ordinary American squad typically has six FP (doubled to twelve for PBF) and a smoke usage number of three (which will be two for WP). Assume that such a squad starts ADJACENT to a Japanese unit in a cave. Which is better: a twelve FP shot up four or a smoke grenade placement? The chart below compares such a shot against a smoke grenade placement by a regular unit with a smoke usage dr of two and an assault engineer with a usage dr of four.

Although these numbers make the WP grenades look great, there are some other considerations. First, the Japanese unit might fire at the unit or units using the smoke grenades. If they manage to lay down good residual in the entrance hex they can disrupt a whole series of placement attempts. But unlike DC placement, smoke grenade placement takes effect before the defender fires, which will reduce the attack and the residual. Smoke in the entrance hex will also reduce the effects of DFF. Finally, a unit placing smoke grenades need not start ADJACENT, and may also fire in the AFPh. [NB: Per G11.85, 1/2" SMOKE in caves persists until the end of the Player Turn; thus, the effect of the smoke grenades persists until the end of the turn, not the phase, adding to the attacker's DRM.] Although an IFT shot can produce a KIA/K result, with the plus four TEM, this isn't likely to substantially affect the results.

>Also NRBH, but do WP grenades locate cave entrances like ordance WP? If so this is another great advantage.

If the other caves are higher, and this is the first WP in the cave, it will reveal the other caves. It's not that this is not good, I just didn't intend to cover all the effects of WP on caves in my little article.

In sum, smoke grenades are surprisingly effective against Japanese in caves. They are especially useful when the attacking units don't start ADJACENT to the cave. A typical attack might put smoke in the entrance hex, then have several units move into the entrance hex and attempt to place WP in the cave. Ideally the units placing WP into the cave would include a leader (which would allow assault movement) and would be concealed (until the smoke placement, of course, but long enough for DFF), then remain in the entrance Location for fire in the AFPh. Even when you can't achieve this ideal, placing WP grenades into a cave should be considered part of the normal approach a cave; I know I'll be using them.

So long,
JR
jrv@mail1.netreach.net

Rodney Kinney adds:

JR has some excellent tips on WP grenades and caves:

> In sum, smoke grenades are surprisingly effective against Japanese in caves.

I would add that from my own experience in Gavutu-Tanambogo, placing WP into caves is a great ploy. The best way I found to use it was if I started with a stack adjacent to a cave entrance, I'd Prep Fire all but one of the squads into the cave. The remaining squad would attempt to place WP grenades into the cave and move away. Then any other squads in range would move up and make a WP grenade attempt.

This is very unnerving for the Japanese player, since each WP attempt carries the risk of a 4MC, like a mini demo charge. He has to fire before he sees the result of the usage dr and the best part is that if he does fire at any of the moving units, then he's halved in Final Fire against the adjacent units. If he really wants to break those two squads and 8-1 leader, he just has to sit there and risk WP attempts from anyone within two hexes. Fun.

JR Van Mechelen: I can't say I've had as much experience as Rodney, but I would think that given the high chance (50/50) of having the grenades land in the cave entrance hex, which would increase the cost of the hex to two MF, that most of the potential smokers would be from one hex range (unless you double-time at start, of course, and per A4.51 this increases the smoke usage dr). But otherwise, an excellent scheme!