Moving under fire: zig zag or sprint?

Azinctus · 09-23-2009, 02:05 PM

My World War One game is going well GURPS is doing a brilliant job of handling the realism. But I have noticed something odd in the rules. It seems moving slowly is safer than moving fast.

Here is an example situation: a piece of ground is under suppressive fire from a machine gun some distance away (e.g. 60 yards). I need to cross four yards of the targeted zone. If I run across that in one turn and the gunner is successful I have a 50 percent chance of not being hit thanks to Dodge 10.

If I take All-Out Defense, half my move of six and take two turns to cross I give the gunner two chances to hit but at ROF 9! and 60 yards he has -7 and probably a less than 50% chance to hit and I increase my chance to Dodge to 74.1%.

Is this correct? Or would he perhaps make four attack rolls for the four hexes + more attacks in his turn (although in darkness and with vision modifiers he has more chance to hit with suppression I think).

I can get silly with this and crouch too. Now my move is just two but he still only gets two shots and he has -2 to hit for my posture.

In GURPS is it sometimes better, when facing firearms, to move slowly? Ducking and diving and zag zagging to put someone off their aim is one thing, but don't soldiers sprint from cover to cover rather than zig zag?

Nymdok · 09-23-2009, 02:24 PM

Quote:

Originally Posted by Azinctus

....It seems moving slowly is safer than moving fast...

Well, we have to look at the complete picture.

Getting shot means his attack succeeds and your defense fails.

LandedHit% = Crit% + (HIt not Crit %)x(Active Defense %)

Your having a dodge of 10 (VERY nice BTW) means that his chance to Land a hit on you is about half his chance of scoring a Defendable Attack.

Rather than increasing your defense, you can also consider penalizing his attack by running FASTER. If your basic move is 7 (6 at a dead sprint) you can hang -3 penalty on him with NO penalty to your dodge AND he only gets one chance to hit you.

Also, giving him 2 turns means he can spend one aiming which aint good for you!

Nymdok

SuedodeuS · 09-23-2009, 02:30 PM

Personally, I don't think hits from Suppression Fire should be Dodgeable without exotic traits (like ETS). The concept behind why you can Dodge normal fire is that you see where the enemy is aiming and get out of his firing arc. That's not exactly doable when someone is just pointing in your general direction and holding down the trigger! Thus, fewer chances to get hit is better than being able to Dodge better against that enemy rifleman covering the machine gunner.

Another reason why soldiers sprint rather than dodge and weave is because if someone is going through the area you're covering slowly, you stop the Suppression Fire and start shooting directly at him! Having a full RoF 18 (or higher) shooting at you isn't fun, even if you can Dodge. And, of course, that machinegunner probably isn't the only guy there, meaning even more shots at you. A final reason soldiers sprint is because trying to dodge and weave (even if it is effective) doesn't feed to the "OMFGRUN!" feeling their body is giving them nearly as well as just, well, running.

Finally, even if you do allow for Dodging, keep in mind you are giving the gunner two chances to hit you (the second of which is likely to focus on you). If he hits with just one bullet each time, that 74% chance to Dodge each turns into a 57.7% chance to Dodge both. This is only a marginal improvement over your normal Dodge, and the chance of multiple hits (or a lucky crit) is higher. All told, you're better off just running it.

Ulzgoroth · 09-23-2009, 02:30 PM

Run in one turn, maybe get nailed by suppressive fire: Not great.

Be evasive in two turns, maybe have someone actually shoot at you rather than just the area you're in: Might be an improvement.

Waddle and take three+ turns, and have somebody (maybe even the machinegunner) aim and fire at you: Extremely unhealthy!

Addendum: I assume dodge 10 means a dodge-and-drop. Once you've done that, getting the rest of the way to cover is going to take a while.

Crakkerjakk · 09-23-2009, 02:57 PM

I would only choose to sprint across a suppressed area if I could cross the area in a second, and even then would very much prefer to find a way around.

If you take any more than a second or two, the gunner has the time to aim specifically at you, and there's a fairly good chance you're toast.

One part of Marine Basic Training is called "Fire Team Rushes." The idea is that you have a squad with three fire teams. While the first and second fire team lay suppressing fire on defensive positions from the prone, the third fire team gets up, runs forward, and then flops down in the best cover they can find. You're supposed to be saying to yourself "I'm up, they see me, I'm down." The time it takes to say that is how long you have to get up, rush forward, and drop back down. Once you're back down, you start suppressing the defensive positions and the next fire team leapfrogs forward in a similar manner.

Anyway, the point is modern military doctrine realizes it is a bad idea to be an easy target long enough for them to aim at you, and it's a good idea to keep rounds zinging around them even if they're in a good defensive position to keep them from getting comfortable enough to calmly draw a bead on you.

In summary. If you're in their sightline for more than a second, they stop doing suppressive fire and start aiming, which dramatically increases their odds of hitting you.

Azinctus · 09-23-2009, 04:20 PM

Thanks for the input guys. If you don't mind I try to describe the situation I'm thinking a little more precisely:

I'm the GM in this game. The situation I picked out is an odd one, but I think it is realistic and somewhat historically accurate. The PCs are hand picked volunteers built on 150 points +30 of disadvantages and 5 quirks so DX 12, HT 12 and Combat reflexes isn't unreasonable. In fact only one of three players actually has dodge ten the others have nine (and one insisted on bringing a gas mask and carrier pigeons so he is encumbered and has eight). But I think even for dodge eight you are still better to take two turns for dodge ten.

It is a night patrol into enemy territory, at one point an illumination flare revealed the PCs position. By the time the machine gunner was ready the flare had gone out, however his position was ideal to lay fire in their general direction which he did. A courageous NPC tired to cross the area of suppresion fire was hit by a critical hit and killed... The PCs were actually able to move away safely.

But it got me thinking about the general situation: its dark, grenades are falling on your current position and the machine gunner is cutting off your retreat. So the question is how best to cross suppressive fire, at night. And it seems that All Out Defense the plus two to dodge (without dodge and drop) is best despite the half move and risking two shots.

While crouching will reduce the chance to hit (-9 for range, +2 for ROF 9!, gives the gunner -7, he has 14 in Gunner (machine gun) so he hits on a 7 or less (16.2%), crouch and he hits on a 5 (4.6%)). Add to that the 74.1 percent chance of dodging and you are better to go slow and give him two shots (not three with crouch and All-Out Defense, half of move six allows you to cross four hexes in two turns while at a crouch).

The extra round in the line of fire doesn't add much danger of being hit even if the enemy has time to target you because of the darkness penalty of -6 for the partially cloudy night with some moon. If he targets you he only hits on a critical. Extra speed won't help because the machine gun is 60 yards away +3 or +6 yards won't worsen the modifiers. The darkness and range penalties mean that the machine gunner can't Wait and hope to spot you he has -15 to his perception roll!

If the machine gun was even further away, at 200 yards or more (100 yards if you're crouching) the gunner would only hit on a critical. At that point you would be better to run fast and not give him two chances to roll a four or less.

Understanding this situation is important because in WW1 much machine gun fire was effectively blind, even indirect. I can understand why SuedodeuS thinks suppression fire ought not be subject to dodge, but I would prefer not to houserule, if I were to houserule it might be more simple to simply disallow All-Out Defense against such random fire.

Maz · 09-23-2009, 04:58 PM

Quote:

Originally Posted by Ulzgoroth

Addendum: I assume dodge 10 means a dodge-and-drop. Once you've done that, getting the rest of the way to cover is going to take a while.

Nah he said he had Move 6, so he probably have Basic Speed 6, so thats 9 dodge, and +1 from the Combat Reflexes that this soldier most likely has. D'n'D would get it to 13! Ad +2 from a feverish defense (if playing with EE in combat) could mean Dodge:15!!

Kromm · 09-23-2009, 05:24 PM

Truly random blind-fire should allow no Dodge roll . . . that's an attack from a source you can't see or anticipate. If bullets just graze into you from across a field or over a rise, they're no different from bullets fired by a concealed sniper or a man standing behind you.

Otherwise, note that the very fact you have a dodge vs. guns at all means you're already doing a zig-zag or similar. You don't need All-Out Defense to explain that. All-Out Defense is more "pause-move-pause-move" behavior, and against guns represents watching the beaten zone travel or the gunman shift his point of aim, and then reacting when you have an opening.

Crakkerjakk · 09-23-2009, 06:40 PM

The way you described the situation, the best approach is to low-crawl (move away in the prone) until you reach some cover to put in between you and the gunner. Then you stand and move away.

carllarson · 09-23-2009, 07:26 PM

My prefered way to penetrate an MG fireplan was to crawl around behind the nest, and spike the gunner's brain.

For the OP's scenario, freeze when the flare lights up. Motion gives you away more than just being a black dot in the field. Then, when the flare burns out, get yourself to cover as fast as you can, and get down. Crawl out of the kill zone, then sneak around to kill the gun.

If you can't break the contact, have half your team place suppression on the MG's firing port, while the other half get into position to frag the nest.

Oh, and often, suppressive fire is grazing fire, so diving on your face, and eating some mud while low-crawling away works. Just keep your bum down.

09-23-2009, 02:05 PM	#1
Azinctus Join Date: Mar 2006 Location: Lyon, France	Moving under fire: zig zag or sprint? My World War One game is going well GURPS is doing a brilliant job of handling the realism. But I have noticed something odd in the rules. It seems moving slowly is safer than moving fast. Here is an example situation: a piece of ground is under suppressive fire from a machine gun some distance away (e.g. 60 yards). I need to cross four yards of the targeted zone. If I run across that in one turn and the gunner is successful I have a 50 percent chance of not being hit thanks to Dodge 10. If I take All-Out Defense, half my move of six and take two turns to cross I give the gunner two chances to hit but at ROF 9! and 60 yards he has -7 and probably a less than 50% chance to hit and I increase my chance to Dodge to 74.1%. Is this correct? Or would he perhaps make four attack rolls for the four hexes + more attacks in his turn (although in darkness and with vision modifiers he has more chance to hit with suppression I think). I can get silly with this and crouch too. Now my move is just two but he still only gets two shots and he has -2 to hit for my posture. In GURPS is it sometimes better, when facing firearms, to move slowly? Ducking and diving and zag zagging to put someone off their aim is one thing, but don't soldiers sprint from cover to cover rather than zig zag? __________________ "wars and storms are best to be read of, but peace and calms are better to endure" Jeremy Bentham

09-23-2009, 02:30 PM	#3
SuedodeuS Join Date: Sep 2008	Re: Moving under fire: zig zag or sprint? Personally, I don't think hits from Suppression Fire should be Dodgeable without exotic traits (like ETS). The concept behind why you can Dodge normal fire is that you see where the enemy is aiming and get out of his firing arc. That's not exactly doable when someone is just pointing in your general direction and holding down the trigger! Thus, fewer chances to get hit is better than being able to Dodge better against that enemy rifleman covering the machine gunner. Another reason why soldiers sprint rather than dodge and weave is because if someone is going through the area you're covering slowly, you stop the Suppression Fire and start shooting directly at him! Having a full RoF 18 (or higher) shooting at you isn't fun, even if you can Dodge. And, of course, that machinegunner probably isn't the only guy there, meaning even more shots at you. A final reason soldiers sprint is because trying to dodge and weave (even if it is effective) doesn't feed to the "OMFGRUN!" feeling their body is giving them nearly as well as just, well, running. Finally, even if you do allow for Dodging, keep in mind you are giving the gunner two chances to hit you (the second of which is likely to focus on you). If he hits with just one bullet each time, that 74% chance to Dodge each turns into a 57.7% chance to Dodge both. This is only a marginal improvement over your normal Dodge, and the chance of multiple hits (or a lucky crit) is higher. All told, you're better off just running it. __________________ Quos deus vult perdere, prius dementat. Latin: Those whom a god wishes to destroy, he first drives mad.

09-23-2009, 02:30 PM	#4
Ulzgoroth Join Date: Jul 2008	Re: Moving under fire: zig zag or sprint? Run in one turn, maybe get nailed by suppressive fire: Not great. Be evasive in two turns, maybe have someone actually shoot at you rather than just the area you're in: Might be an improvement. Waddle and take three+ turns, and have somebody (maybe even the machinegunner) aim and fire at you: Extremely unhealthy! Addendum: I assume dodge 10 means a dodge-and-drop. Once you've done that, getting the rest of the way to cover is going to take a while. __________________ I don't know any 3e, so there is no chance that I am talking about 3e rules by accident.

09-23-2009, 02:57 PM	#5
Crakkerjakk "Gimme 18 minutes . . ." Join Date: Sep 2005 Location: Albuquerque, NM	Re: Moving under fire: zig zag or sprint? I would only choose to sprint across a suppressed area if I could cross the area in a second, and even then would very much prefer to find a way around. If you take any more than a second or two, the gunner has the time to aim specifically at you, and there's a fairly good chance you're toast. One part of Marine Basic Training is called "Fire Team Rushes." The idea is that you have a squad with three fire teams. While the first and second fire team lay suppressing fire on defensive positions from the prone, the third fire team gets up, runs forward, and then flops down in the best cover they can find. You're supposed to be saying to yourself "I'm up, they see me, I'm down." The time it takes to say that is how long you have to get up, rush forward, and drop back down. Once you're back down, you start suppressing the defensive positions and the next fire team leapfrogs forward in a similar manner. Anyway, the point is modern military doctrine realizes it is a bad idea to be an easy target long enough for them to aim at you, and it's a good idea to keep rounds zinging around them even if they're in a good defensive position to keep them from getting comfortable enough to calmly draw a bead on you. In summary. If you're in their sightline for more than a second, they stop doing suppressive fire and start aiming, which dramatically increases their odds of hitting you. __________________ My bare bones web page Semper Fi

09-23-2009, 04:20 PM	#6
Azinctus Join Date: Mar 2006 Location: Lyon, France	Re: Moving under fire: zig zag or sprint? Thanks for the input guys. If you don't mind I try to describe the situation I'm thinking a little more precisely: I'm the GM in this game. The situation I picked out is an odd one, but I think it is realistic and somewhat historically accurate. The PCs are hand picked volunteers built on 150 points +30 of disadvantages and 5 quirks so DX 12, HT 12 and Combat reflexes isn't unreasonable. In fact only one of three players actually has dodge ten the others have nine (and one insisted on bringing a gas mask and carrier pigeons so he is encumbered and has eight). But I think even for dodge eight you are still better to take two turns for dodge ten. It is a night patrol into enemy territory, at one point an illumination flare revealed the PCs position. By the time the machine gunner was ready the flare had gone out, however his position was ideal to lay fire in their general direction which he did. A courageous NPC tired to cross the area of suppresion fire was hit by a critical hit and killed... The PCs were actually able to move away safely. But it got me thinking about the general situation: its dark, grenades are falling on your current position and the machine gunner is cutting off your retreat. So the question is how best to cross suppressive fire, at night. And it seems that All Out Defense the plus two to dodge (without dodge and drop) is best despite the half move and risking two shots. While crouching will reduce the chance to hit (-9 for range, +2 for ROF 9!, gives the gunner -7, he has 14 in Gunner (machine gun) so he hits on a 7 or less (16.2%), crouch and he hits on a 5 (4.6%)). Add to that the 74.1 percent chance of dodging and you are better to go slow and give him two shots (not three with crouch and All-Out Defense, half of move six allows you to cross four hexes in two turns while at a crouch). The extra round in the line of fire doesn't add much danger of being hit even if the enemy has time to target you because of the darkness penalty of -6 for the partially cloudy night with some moon. If he targets you he only hits on a critical. Extra speed won't help because the machine gun is 60 yards away +3 or +6 yards won't worsen the modifiers. The darkness and range penalties mean that the machine gunner can't Wait and hope to spot you he has -15 to his perception roll! If the machine gun was even further away, at 200 yards or more (100 yards if you're crouching) the gunner would only hit on a critical. At that point you would be better to run fast and not give him two chances to roll a four or less. Understanding this situation is important because in WW1 much machine gun fire was effectively blind, even indirect. I can understand why SuedodeuS thinks suppression fire ought not be subject to dodge, but I would prefer not to houserule, if I were to houserule it might be more simple to simply disallow All-Out Defense against such random fire. __________________ "wars and storms are best to be read of, but peace and calms are better to endure" Jeremy Bentham

09-23-2009, 05:24 PM	#8
Kromm *GURPS* Line Editor Join Date: Jul 2004 Location: Montréal, Québec	Re: Moving under fire: zig zag or sprint? Truly random blind-fire should allow no Dodge roll . . . that's an attack from a source you can't see or anticipate. If bullets just graze into you from across a field or over a rise, they're no different from bullets fired by a concealed sniper or a man standing behind you. Otherwise, note that the very fact you have a dodge vs. guns at all means you're already doing a zig-zag or similar. You don't need All-Out Defense to explain that. All-Out Defense is more "pause-move-pause-move" behavior, and against guns represents watching the beaten zone travel or the gunman shift his point of aim, and then reacting when you have an opening. __________________ Sean "Dr. Kromm" Punch <kromm@sjgames.com> *GURPS* Line Editor, Steve Jackson Games My DreamWidth [Just *GURPS* News]

09-23-2009, 06:40 PM	#9
Crakkerjakk "Gimme 18 minutes . . ." Join Date: Sep 2005 Location: Albuquerque, NM	Re: Moving under fire: zig zag or sprint? The way you described the situation, the best approach is to low-crawl (move away in the prone) until you reach some cover to put in between you and the gunner. Then you stand and move away. __________________ My bare bones web page Semper Fi

09-23-2009, 07:26 PM	#10
carllarson Join Date: Feb 2005	Re: Moving under fire: zig zag or sprint? My prefered way to penetrate an MG fireplan was to crawl around behind the nest, and spike the gunner's brain. For the OP's scenario, freeze when the flare lights up. Motion gives you away more than just being a black dot in the field. Then, when the flare burns out, get yourself to cover as fast as you can, and get down. Crawl out of the kill zone, then sneak around to kill the gun. If you can't break the contact, have half your team place suppression on the MG's firing port, while the other half get into position to frag the nest. Oh, and often, suppressive fire is grazing fire, so diving on your face, and eating some mud while low-crawling away works. Just keep your bum down.