Ground Assault Procedure in GOSS

We are still dissecting and digesting the rules for the Grand Operational Simulation Series. But the hard part is almost done.
So you moved your guys in position, made sure they have fuel and ammo, you even sent a few artillery volleys over into the target hex, now what? It’s time to dig into the Ground Assault (GA) rules.
The rules for Ground Assault cover some eight pages. But, no panic! It’s really not that bad. There are a few concepts that are not necessarily found in other games. But that doesn’t mean the Ground Assault rules are complicated (Spoiler: They are not!). Let’s try to break the procedure down into bite-sized pieces.

The Ground Assault Sequence

A quick look at the Sequence of Play tells us that a Ground Assault takes place during a player’s Combat Phase, the second to last phase in a player’s turn:

  1. Air Allocation Phase (AM)
  2. Weather Determination Phase
  3. Command Phase (AM)
  4. Transport & Logistics Phase (AM)
  5. Allied Player Turn
    1. Allied Mode Determination Phase
    2. Allied Construction Phase
    3. Allied Movement Phase
    4. Axis Exploitation Phase
    5. Allied Combat Phase
    6. Allied Administration Phase
  6. Axis Player Turn (see above, reverse roles)
  7. Game Turn Complete

We saw this already during the presentation of the Fire Support rules, the Grand Operational Simulation Series is very procedural and the Ground Assault is no exception. There are seven steps to each Ground Assault. If there are several Ground Assaults to be resolved, the active player (attacker) has to finish one assault before proceeding to the next one. The seven steps are as follows:

Step 1: Identify Defending Hex Terrain

This one is straight forward. In case of multiple terrain forms in the target hex, the defender decides which terrain to choose. The terrain can then be cross-referenced in the upper part of the Ground Assault Table (GAT):

The Ground Assault Table might look intimidating at first. But it’s just big because it has three parts. The upper part is the terrain part.

What information is provided here? Let’s assume you attack an opponent in a Village hex, then this table tells you that you will have to use Line 2 when it comes to combat ratios (see below).

Step 2: Who is attacking?

The active player indicates the units that participate in the assault. Both players have to name one unit as the lead unit, the unit that will take the first hit but also determines the proficiency of each side.

Step 3: Any last minute surrenders, demolitions, etc?

If the defending units are Isolated and Out of Supply, they need to pass a Proficiency Check in order to not surrender.


The defender also has a chance to destroy bridges before the combat, making it impossible for Mechanized Units to participate in the Ground Assault. The probability for a successful (Hasty) Bridge Demolition is a function of the involved engineer steps.

Step 4: Calculating the Ground Assault Value

Like the Fire Support procedure, the Ground Assault procedure requires a little bit of math. Nothing complicated but have a piece of paper ready just for bookkeeping purposes.

Both sides add now their attack/defense values. The values can be modified due to terrain, supply status, or due to a unit’s Fatigue. Additional penalties can occur when attackers do not follow a Combined Arms Doctrine and throw only armor at the defender.

The ratio of the two strength values is then the Ground Assault Value (GAV). Together with the Terrain Line from Step 1, we can then find the column for our die roll in the Ground Assault Table:

With the terrain effect from step 1 and the ratio of Ground Assault Values you can pick the column that will determine the outcome of the attack.

Step 5: Determine Number of Column Shifts

But before we can roll any die, we need to determine if there are any Column Shifts that have to be taken care of. There’s a sizeable list of conditions that lead to Column Shifts that either favor the attacker or the defender.

Have a look at the table if you want to know more details about when those shifts occur. Don’t try to memorize them, you will be better served running through them like a check-list during a Ground Assault.

GA Column Shift Conditions

All shifts are cumulative, so these shifts can have a major effect on the battle. As a matter of fact, those shifts can change the sign of the battle. If you play your cards right you might be able to pull off an assault despite an unfavorable Ground Assault Value.

Let’s stop here for a minute to remind ourselves what a Column Shift actually means in terms of combat factors. Going from a Ground Assault Value of n:1 to (n+1):1 (a Right shift) is identical to adding attack factors in the amount of the total number of defense factors. So an R shift adds attack factors in multiples of the defence factors. This is quite powerful! And of course, you can play the same game for L shifts or when the ratio is inverted.

Step 6: Determine the Die Roll Modifier

The Column Shifts are awarded for external conditions like the unit mode, units using fortifications, supply status or the presence of engineers. A little more subtle but no less decisive are the Die Roll Modifiers (DRM) that depend on the internal mechanics of the battle. DRM are granted in four different categories. In each category attacker and defender can collect bonus points. Depending on the category each bonus point is worth 5-10 DRM points. The following table gives an overview of the categories.

Ground Assault DieRoll Modifiers are awarded in four different categories. They are cumulative and can easily have the effect of several column shifts.
  • Combat Reserve: Up to three battalion-sized infantry units in Combat Reserve not further away than three hexes from the Ground Assault contribute 1 bonus point (5 DRM points.) each.
  • Regimental Integrity Bonus (RIB): RIB points are awarded to units belonging to the same sub-formation (usually regiment), simulating the fact that those units tend to work together more efficiently. The attacker can collect RIB for two regiments, the defender for one. Each RIB bonus point is worth 5 DRM points.
  • Proficiency: The difference of attack and defence proficiency values of the two lead units (see above) translates into bonus points that are worth 5 DRM points as well.
  • Armor/Antitank: The presence of armor and/or antitank units results in yet another DRM. The calculation of the bonus points takes into account on which side the armored and antitank units fight.

The total DRM is calculated by adding all attacker DRM points and then subtracting all defender DRM points. A resulting positive DRM will be added to both the attacker and the defender DR, a negative DRM is subtracted from both DR.

I’d like to emphasize the overall-effect of Column Shifts and DRM on the simulation. They both lead to a very nuanced battle. Two different Ground Assaults with identical Ground Assault Values will unlikely lead to the same outcome. It won’t be enough to just pile up combat factors around the target hex. Comment Shifts and DRM add another dimension to the Ground Assault that needs to be taken into account!

Step 7: Roll Dice and Implement Results

We have the Ground Assault Value, the column shifts and the DRM. Now both players roll 2d10. And both players apply the same DRM to their results. While the attacker tries to roll high, the defender needs low numbers.

This is just a small thing, but I really love the idea that the attacker and the defender roll dice. Not only will this produce more detailed results, I like that it leads to a real interaction between the players.

As you can see the Ground Assault Table is split in half for attacker and defender. The result can be read in the Results column that is nearest to the right of the modified DR (There are two results columns, modeling an increase in the odds when going to larger ratios.).

GOSS Ground Assault Table, GAT
The complete Ground Assault Table.

There are four different results possible: no result, Proficiency Check, Mandatory Hits and Discretionary Hits. The Proficiency Check is made against the Lead Unit‘s proficiency. If the unit fails the check an additional Discretionary Hit is added to the result.

How to apply those hits now? You start with the Mandatory Hits. They are taken as step losses! During a Ground Assault, the Maximum Step Loss rule applies. That means no unit can lose more than one step. Losses are taken according to a priority list: lead Proficiency unit -> lead Armor/AT unit -> engineers (if used for their engineer capabilities) -> non-HQ, non-artillery units -> …

Under certain circumstances, Mandatory Hits can be transformed into Discretionary Hits. For example, each Recon or Commando unit can convert one hit. Non-attack designated defenders can use their ET-3 fortification to convert one Mandatory Hit.

All remaining Mandatory Hits are eventually converted to Discretionary Hits. Those are then resolved by first retreating (reduce Discretionary Hits by 1 for each hex retreated), then inflicting further step losses (obey max. step loss rule) and finally are absorbed as Fatigue Hits (see Resolving Artillery Hits). If all units retreated the maximum distance, took their maximum step loss and accumulated their maximum in Fatigue Hits the procedure ends and the remaining Discretionary Hits are omitted. After passing a Proficiency Check units can voluntarily convert their Discretionary Hits.

Advance After Ground Assault

This should be actually Step 8. If the defender (!!!) vacates its hex, the attacker has the chance to advance. This is not part of the movement segment and does not depend on the Movement Allowance of units. Instead, the unit’s Mode determines the maximum distance. In Tactical Mode units advance up to one hex, leg units in Prepared Assault Mode can advance two and mechanized units in Prepared Assault Mode up to four hexes. Until the defender is eliminated during the retreat, the advance path has to follow the defender’s retreat path.

And this concludes the Ground Assault procedure. Don’t feel intimidated by the eight pages of text needed to describe the procedure. Read the chapter once and then try to apply the procedure in the Bloody Bucket intro scenario. You might have to re-read some sections, but do not expect any major headaches because of bad explanations or inconsistencies.

Final Thoughts

28th Infantry Division troops advance through the Hürtgen Forest
28th Infantry Division troops advance through the Hürtgen Forest in Germany on November 2, 1944. (PFC G. W. Goodman/U.S. Army/National Archives)

We saw already that the GOSS Fire Support rules try to create a very nuanced simulation. The Ground Assault procedure follows the same standard. I can understand that for some players this level of detail is not tolerable. The game starts to take a backseat and procedures and their checklists take over. But for the players who do not mind, who accept these additional efforts to be part of the game, can expect a very deep game experience.

I like a lot that unit types have a ‘role to play’. Starting from the combined arms doctrine, over engineers offsetting the effect of fortifications to recon units that are agile enough to draw mandatory hits and convert them to discretionary hits. All of a sudden preparations for an assault become more than planning to accumulate attack factors around a target hex.

You probably see where this is going. I’m really impressed by this system. Last week I started playing the second scenario of Hurtgen: Hell’s Forest. Unlike the intro scenario, it covers all rules. I’m still far from being super confident in what I’m doing yet I’m enjoying it quite a bit. I’m looking forward to sharing an AAR at a later point.

We have now covered all major rules for the Grand Operational Simulation Series. But we are not done yet. If you like, come back next time when I will go through those rules that ’round off’ the game system.

Abraços,
Carsten