Mortars vs Artillery

[kalos72]

Question...obviously range is a big difference but is there a "use" or "design" difference between say a heavy mortar and a towed howitzer

[CDAT]

I am not now, and never have been a red leg, but my understanding is that the arc of fire is also a big difference.

[Webstral]

I'm not a red leg either, so my knowledge has real limits.

As CDAT points out, the ballistic trajectory of the round is dependent upon the type of artillery used to fire it. The higher the muzzle velocity, the flatter the trajectory of the round. Flatter trajectory means longer range, all things being equal.

The category Field Artillery includes two types of tube artillery: field guns and howitzers. Field guns achieve higher muzzle velocity than howitzers, As a consequence, field guns have comparatively longer ranges. The flat trajectory of fire from a field gun means that the gunners can't hit targets behind a hill. Howitzers, with their lower muzzle velocity, can be used to hit targets behind a hill but suffer from range limitations.

Mortars, with their comparatively low muzzle velocity, have several advantages over their cousins in the field artillery. The high arc trajectory of a mortar round in flight means the crew can put mortar rounds into a trench. Obviously, they have to know what they are doing to make this happen at ranges of 1km or more. Still, the high angle of descent of the round makes getting an HE round into the enemy's trench feasible, if not very easy. This very possibility is what brought mortars back into common use in WW1.

One advantage of the low muzzle velocity of the mortar round is that the firing of the round develops a much lower pressure compared to the pressure generated inside a howitzer or field gun. Consequently, mortars can be much lighter than a howitzer or field gun firing a shell of equal caliber. Also, the shell casing of a mortar round can be made thinner than the shell casing of a field artillery round of equal caliber. A 120mm mortar round would pack more HE than a 120mm howitzer round, if there were a 120mm howitzer round. So a 120mm mortar unit is useful for really delivering punishment out to 5km, whereas the markedly smaller 105mm howitzers pushes its rounds out much further.

Again, I'm no red leg, so you have to take my somewhat anecdotal observations about mortars v field artillery with salt. When I have looked at fire mission planning for the 120mm mortars that are assigned to heavy battalions versus the missions assigned to the 155mm field pieces supporting a brigade, the mortars fire more smoke per tube. One has to bear in mind that these two IF systems are apples and oranges. In US doctrine, medium and heavy mortars are often assigned at battalion level in platoons of 4-6 tubes. Howitzers and field guns typically are organized as battalions of 18-24 tubes assigned to brigades or larger formations. The concept of use is derived from the characteristics of the pieces.

It's a shame I'm not with my NG infantry unit anymore (other than the fact that had I stayed with them I'd have done a second tour in Iraq and a tour in Afghanistan by now). I'd be able to call on one of the mortarmen for better answers.

[kalos72]

Great info, thanks guys.

From the doctrine perspective, I wonder if it was just the feeling a battalion didnt need to reach out and touch someone at 15km since that would be outside its AO

In my game, light battalions, with additional heavy weapon support, are assigned a county. Currently they are given light mortars at the platoon level and 4.2's at the battalion level. I was wondering given their typical AO, if heavy fire support would be needed.

[ArmySGT.]

Question...obviously range is a big difference but is there a "use" or "design" difference between say a heavy mortar and a towed howitzer

Cannon are direct fire. Howitzers are indirect fire. Mortars threw a bomb over a wall or high enough upward to fall straight down and not at an angle. This got a bomb into a trench work or to impact near the base of the wall on the defenders side. Mortar bombs are lower velocity and pound for pound often have greater explosive filler than a shell.

Early blackpowder breech loading mortars are massive to absorb the detonation of an explosive bomb in the breech should one prematurely detonate. Mortars came before howitzers until explosive shells had matured enough to not blow up in gun barrels destroying them. Howitzers also came about as the defenses were built and manned further out creating more depth in the defense that was outside the maximum range of many mortars.

[unkated]

The other trick is that light mortars (50-81mm) are small enough that they do not require any specialized means of transport, so to attach them at company or battalion level does not require a peculiarity in the TO&E, or an attachment, nor does it require specialists from another branch of the army - mortarmen are infantrymen.

The point is to provide the battalion some extra support at a low tactical level, where the response time is very short. And, yes, the range on light mortars is more likely to be directly applicable to the needs of the battalion or company.

Once upon a time, Regiments had a gun section for the same reason.

Uncle Ted

[swaghauler]

The US Army has no proper "field guns." A field gun was a WW2 term for a towed Anti-Tank gun. the Russian 37mm, 57mm and 76mm WW2 Anti Tank guns were "field guns." The US embraced the concept of a "general utility platform" for its artillery after WW2. This was based on observations about the German use of the 88mm Flak gun as an AT gun, an AA gun, and a fire support weapon. The Army later dropped any AA missions from the field artillery.
The US Army did continue the concept of a multipurpose gun with regards to AT and fire support. Both the M102 105mm GUN/HOWITZER and The M198 155mm GUN/HOWITZER that I served on with the 10th Mountain had HEAT warheads and the M198 could fire the Copperhead laser guided AT missile. Both the HEAT and The Copperhead could be fired indirectly if needed. You would fire the HEAT at an extremely steep angle to induce plunging fire (for bunkers) and the Copperhead would stabilize itself in flight. Mortar crews were just our little brothers. We were even slated to begin using the same fuses in our rounds (they were converting over to ours). While AT missions were part of our training; I would not have wanted to do it in real life. Our guns had manual traverse and elevation. Our 155mm shells weighed 96 lbs and we had a maximum effective range of 18km with conventional shells. The newer "base bleed" shells (which generated a gas vortex behind them) were good for about 22km (depending on the shell- HE, GAS, HEAT, etc..) our enhanced RAP rounds (rocket assisted projectile) were good for almost 40km but our Circular Probability of Error (CEP) increased significantly. The CEP of conventional shells was about 100 meters around intended impact point. Newer low drag and base bleed rounds brought that down to 30 meters CEP at 15Km and about 50 meters CEP at maximum IFR.

It is important to note that the rounds a 105mm, 155mm, or 203mm Howitzer fired travel at just under 900 meters a second. it would take TEN SECONDS for a round to travel 9km. The IFR rules in Twilight2000 should take this into account.

In my game it takes 1 minute to call a fire mission plus 2 rounds to fire the gun. I then add the appropriate flight time. My players will often "make a stand" to give the FO time to "call fire." The FO also is required to have a Topo Map and a compass in order to call fire (he must determine the enemy's grid coordinates). My players made the FO the navigator as well.

When determining hit location of rounds; I use 1d20 - FO's roll under skill/hit chance X 5m for deviation of the rounds (0 means an "ATTABOY!, or direct hit- these are much coveted in the artillery) with a CEP of 100m. I use 1D6- FO's roll under his skill/hit chance X 5m for rounds with a CEP of 30m. On a miss; I add the amount missed by to the CEP roll.
I also divide the Indirect Fire Range into 4 range bands which add (12km IFR becomes SHT-3km, Med-6km, Lng-9km, Ext-12km) with appropriately decreasing to hit skill to represent the difficulty of long range fire.

I hope this helps you out.

Swag

[kalos72]

Nice details swag!

Unkated - I am thinking of moving the heavy mortars to the company level and adding 2-3 towed pieces to the battalion level.

Anitarmor/scouts are at the battalion level as well.


Thoughts

[Askold]

The other trick is that light mortars (50-81mm) are small enough that they do not require any specialized means of transport, so to attach them at company or battalion level does not require a peculiarity in the TO&E, or an attachment, nor does it require specialists from another branch of the army - mortarmen are infantrymen.

The point is to provide the battalion some extra support at a low tactical level, where the response time is very short. And, yes, the range on light mortars is more likely to be directly applicable to the needs of the battalion or company.

Once upon a time, Regiments had a gun section for the same reason.

Uncle Ted

I think that is their main selling point.

A cannon with the same firepower would be much heavier and need to be transported by vehicles. Meanwhile there are mortars that are light enough to be carried by one person (WW2 had some tiny mortars being used...)

Grenade launchers and grenade machineguns also offer firepower to infantry units but having a few 81mm mortars a kilometer or two away from you does offer nice fire support AND they can usually reach far enough to help another company in the battalion AND the ammo is usually more versatile. (HE, WP, Flares, smoke and so on.)

[kalos72]

Good point about the gl's...

Maybe move the MG's straight into the squads, GL's to the weapons squads, 60 mm to the mortar section at the platoon level, 120's at the company level and 4 towed 105mm at the battalion level

I never really got the SAW v MG line, not being infantry. Sure different calibers, rof and such but are they that much different to need a special section for them

Maybe have the weapon section on the platoon level with 2 HMMWV's with Mark-19's instead of M60's Didnt the Vietnam era squads carry the mg's organically

[unkated]

Good point about the gl's...

Maybe move the MG's straight into the squads, GL's to the weapons squads, 60 mm to the mortar section at the platoon level, 120's at the company level and 4 towed 105mm at the battalion level

I never really got the SAW v MG line, not being infantry. Sure different calibers, rof and such but are they that much different to need a special section for them

You're not thinking in terms of weight. Somebody has to carry this stuff. Infantry should always plan in terms of having to walk to where it will fight - meaning carrying stuff.

Mortars usually break down into three parts (tube, base plate, bipod)

The M224 60mm mortar weighed some 21 kg altogether, and that was a light weight design. That's 15 lbs for 3 guys, before you start adding shells.

A simple 81mm mortar, say the M252 of the late 1980s (a copy of the British L16), is 40 kg; each shell is 3-6 kg.

Heavier mortars need a vehicle, either to tow a wheeled or have on board. The M120 (current 120mm) mortar is 145 kg - 300 lbs; the shells are some 12.5-13.65 kg apiece.

The weight difference between an MMG and an SAW is less pronounced than it used to be, but, for teh same weight, you can carry a LOT more ammo with a SAW; and for NATO-compatible armies, it means that the SAW and your longarms fire the same ammo.

Uncle Ted

[Raellus]

My dad had personal experience with both types of tube artillery. He was an FO for a battery of 105mm howitzers during the first year of the Korean war. He was wounded by a North Korean mortar. He claimed that conventional tube artillery one could hear coming (a sound akin to the distinctive whistle and/or rumble one hears preceding the impact of artillery in war movies) but mortar bombs one typically could not, making being on the receiving end of an unexpected mortar barrage particularly terrifying.

-

[swaghauler]

Composition and Tactics of an Artillery Unit.

I've posted this once before but I'll post it here again.

An Artillery Battalion consists of 3 Gun Batteries, 1 HQ Battery, and a Service/Support Battery. The Standard Gun Battery is equipped with the 155mm (6"). The standard gun for Armored and Mechanized Infantry units was the M109 SP gun. The Standard Infantry Division was equipped with the M114 Towed Howitzer until the 80's. It was then replaced by the M198 Towed Gun/Howiter. Light Batteries would possess the M102 Towed 105mm until 1990. The British 105mm Light Gun (designated the M119) replaced it after 1990. These are almost exclusively attached to air mobile or airborne units after the Army disbanded all of its light infantry divisions (with the exception of the 10th Mountain and the Arctic Division). The Heavy Batteries were attached to Armored and Mechanized Divisions at the rate of ONE per division. They used the 203mm M110 SP gun. The standard compliment of a Gun Battery before the 80's was two "Smokes" (platoons) of 3 guns each for 6 guns per battery. When the Army reorganized the Field Artillery in the 80's; The 155mm and 105mm Batteries got 8 guns each in 2 "smokes" per battery (this was part of the "Division 86" protocol). The Heavy Batteries kept two (6) Gun Batteries as standard but added an MLRS Battery consisting of 9 launchers (with 3 "smokes") in addition to the guns (for a hybrid 3 Battery configuration of 9 launchers and 12 guns).

Mechanized Batteries contained (in addition to their guns):

1 FASV Ammo Carrier per gun (heavy gun units used M548 cargo variant of the M113). MLRS had their own specialized ammo vehicle.

1 M577 Command Vehicle for Fire Direction and control. Later versions in the Army were equipped with Radar for threat detection and counter battery fire.

1 Command Humvee
2 Utility Humvees (1 for advanced party, 1 for XO/Commo)

1 NBC Humvee complete with M8 Chemical Detector and Fire Fighting gear (specialized for WP rounds)

1 Tracked Recovery Vehicle Detached from Service Battery and under orders to service emergency needs of the gun battery.

1 Supply/Utility 5-ton
1 Advanced Party/Utility 5-ton (for the advanced party)
1 HEMMETT heavy Utility transport or 5 ton (for the Battery mechanics)

The 155mm Towed battery made the following changes:

1 5-Ton per gun
1 HEMMETT ammo carrier per gun (later versions of these were lightly armored)

1 HUMVEE FDC vehicle (later there were 2; one with counter battery radar)
1 Command HUMVEE
1 Commo/XO HUMVEE
1 NBC HUMVEE (with M8 detector)
1 Utility HMVEE (for advanced party)

4 5-ton trucks for 2 Maintenance, 1 Supply, 1 Advanced Party/utility.
1 HEMMETT Recovery vehicle detached from Service Battery.

Light Gun Batteries had the following vehicles:

2HUMVEES per gun (one for towing, one for ammo)

1 5-ton Wrecker/Recovery in place of HEMMETT wrecker.

The Army began operating Gun Batteries as "Autonomous Units" in the 80's Both HQ and Service batteries would detach important personnel among the batteries. Each battery could operate "without support" from other members of the battalion. Service Battery had a dual role. Service and recovery of breakdowns/battle damage AND supply of the forward batteries with fuel and ammo. The Battery's Recovery section moved with their assigned Gun Battery. The Supply section had dedicated Tankers and HEMMETTs for each Gun Battery that would move "beer, bullets, and beans" to that battery from the rear areas. This way, a Gun Battery could concentrate on Fire and Displacement.

The Army would have one Gun Battery Displacing while the other two Gun Batteries provided fire support. This allowed [8 guns X 2] to "respond" to calls for fire support. Since a battery only had 1 FDC team; Each Gun Battery would respond to only one call for fire support.

When a Battery (any battery) displaced; It would send an advanced party to survey and prep the area it was displacing to. This was known as an Advanced Party or RSOP (Recon, Survey, Occupation, & Preparation) Team.
HQ would have a survey crew with each Gun Battery who would mark its location with a Transit (for surveying). When the Guns arrived they would "Lay" using a device called a Collimeter. This telescopic like device was used to determine a gun's Deflection (horizontal Arc) and quadrant (vertical Arc/Range to target). If a gun was doing a "hip shoot" (an unsurveyed shoot) off of just "Aiming Stakes" (2 colored poles which fix your position in the world) or a DAP (distant aim point- a pole, tree, or structure); The difficulty would be one level greater.

Batteries which receive "casualties" would be reorganized into smaller 6 or 8 gun batteries. This is because of the nature of fire support. When support is called; 3 guns will fire forming a triangle in the impact area. The idea is to overlap each gun's CEP (circular error, probable) to enhance damage in the "kill box." The Army went to 4 gun "smokes" to increase the lethality of the "kill box" by putting 1 round on each corner of the impact area (giving a 4 CEP overlap).

By the time of the Twilight War. Individual units would be able to call for fire support from any available Artillery Battery without the need to "go through channels." The only issue would be what support was available.

Availability of Support (1D100):

Item Available:
Nothing Available: 71-100 (US), 81-100 (PACT)
60mm Mortars: 51-70 (US)
81mm/82mm Mortars: 41-50 (US), 61-80 (PACT)
105mm/120mm Mortars: 31-40 (US), 46-60 (PACT)
105mm Howitzer 26-30 (US)
122mm Rockets: 41-45 (PACT)
122mm Howitzer: 31-40 (PACT)
152mm/155mm Howitzer: 5-25 (US), 10-30 (PACT)
203mm Howitzer/MLRS: 1-4 (US)
Soviet 203mm Howitzer/Rockets: 5-9 (PACT)
240mm Mortar: 1-4 (PACT)

This is just an example chart of the availability of Artillery on a major front.

[Webstral]

Nice layout above!

Its true that the US Army does not have any field guns in its inventory at the present. The last field gun was the M107 175mm self-propelled gun. This system was replaced in its role providing long-range fires by field artillery rockets by the 1980s. However, the M107 was widely exported to US allies. In Twilight: 2000, this system might be found with German, Iranian, Greek, South Korean, and British formations, among others.

http://en.wikipedia.org/wiki/M107_self-propelled_gun

[kalos72]

Swag has all the 411!

The mortar teams would have an unarmored cargo vehicle of some sort...adjusted to meet the needs of the weapon.

This is a custom build unit for III Corps return to the US to clean up Texas. My units were smaller, battalion sized, and carried more punch at lower levels. IE the mortars at the platoon level.

My question is really would a pair of howitzers be of much use to a battalion that already has 4 heavy tubes and is only responsible for a single county Might be overkill...

Also, that whole MG v SAW thing at the squad level still irks me. I like the same ammo point...but is the firepower that much different at this point

Would GL's make better use of a weapons squad maybe