Impetus and Basic Impetus

November 2, 2011

After a long hiatus, I finally have for you a review of Impetus by Lorenzo Sartori of Dadi & Piombo.  Impetus is a game of massed combat using large and chunky elements.  The author aims to provide a simple but fun game of Ancient combat while also providing a good looking table top of miniatures.

The Book

Impetus comes as a spiral bound book printed in full color on heavy stock paper.  The book is 50 pages long and has numerous photos for inspiration and diagrams that help to illustrate how the game is played.  There are army lists at the end of the book and there is a points system published online.  There are also several supplement book which provide more army lists as well as campaigns and historical backgrounds.


In general two armies broken up into a number of commands is required to play Impetus.  This will usually be 100 + figures when using 15mm figures in the suggested base sizes.  I used DBA stands to represent units and use the smallest scales (1U=1cm).  The game played fine.

Before the battle can commence, the players will go through the setup routine to set out terrain.  This is a very simple but effective process.  Players will each throw 2 dice.  High roller is the attacker.  The defender will place 2-4 pieces of terrain.  The attacker will then have the option to move or remove 1 piece of terrain.  There is a chance for a built up area (village) and a river.  The defender will throw 1 die for each.  If a 5+ comes up, that terrain piece is also available in the mix.  Like I said, simple but effective.

The Rules

Impetus has an unusual turn order.  As stated before, each army is broken into a number of commands, usually 2-4.  Each command has a general with a leadership modifier based on how effective the general is.  Each player nominates a commander to move, rolls 2 dice and compares the results.  The high roller must move.  The player moves, shoots and melees with all units in that command.  Once he is done, both players nominate another command to move.  Once all commands have moved, a new turn begins in the same fashion.


A player nominates a unit or group of units to move.  The units may move straight ahead or wheel.  They may do both but risk disordering the unit or group.  The first move or wheel is ‘free’.  Each subsequent move or wheel the player rolls a die and compares to the discipline number for the unit.  If it is less than that number, the unit is disordered and may not move again.  Each move increases the chance of failure by 1.  Commanders can influence the discipline roll if they are part of the unit or group making the roll.

There are some reaction moves that can be done if a unit enters the zone of control (5U in front of the inactive players unit).  For instance, if a unit makes a move not directly at the enemy unit, the enemy could take a shoot of opportunity.   As well, a unit could be placed on opportunity and be allowed to interrupt the enemy with an opportunity charge or a shot of opportunity.

When charged, light cavalry and skirmish infantry may evade away from the charger 1 move.  Pretty standard stuff.


All combat in Impetus and Basic Impetus is done using the same game mechanic.  Each unit is rated with a ‘Basic Unit Value’ or ‘VBU’.  This number will range from as low as 2 to as many as 8.  The higher the number the better.  To this are added tactical and support bonuses for other units and situations as well as the impetus value (I) if the unit is charging and is fresh (has not taken any hits).  An attack invloves rolling dice equal to the modified VBU.  For each ‘6’ or pair of ‘5s’ rolled, one hit is registered.   The player owning the target unit must now roll a cohesion test.  The number is the target units VBU minus the number of hits received.  A ‘1’ always passes and a ‘6’ a;ways fails.  If the die roll is greater than the target number, the difference is the amount of permanent damage the target unit receives.   The target unit VBU is reduced by this amount.  Both sides of a melee get to fight before damage is recorded.  The unit that takes the most permanent damage is the loser of the combat.  It retreats a variable amount.  The attacker may pursue a variable amount.  If the attacking unit catches the target unit, another melee immediately begins.

Missile combat is a little different.  As well as tactical modifiers, there is a bonus or penalty for the type of weapon used depending on the range to the target.  There is a vast array of missile weapons rated in the game.  Missile combat is not simultaneous.  The attacker only causes damage to the target.

Regardless of combat, when a unit takes hits, whether it passes a cohesion test or not, that unit is disordered.  If it was already disordered and passes a cohesion test, it take 1 point of permanent damage. Damage from accumulated disorder is not considered when determining the victor of a melee.

Large units are an interesting aspect of Impetus.  Warbands and Hoplites can usually form two units deep and Phalangites (Pikes) can form four units deep.  The effect of these large formations is to give the front unit extra dice for each additional rank.  The back unit takes damage based on the cohesion of the front unit and is eliminated first.  The whole unit is not worn until the front unit actually takes damage.  If a large unit is flanked and subsequently fails a cohesion check, the whole unit routes.

Winning and Losing

The game is over when one side has reached its breakpoint in ‘Demoralization Value’ or ‘VD’.  Each unit in an army has a VD.  One half the sum total of the VD is the break point for the army.  As untis are eliminated, the VD of that unit is deducted from the total VD for that army.  When the total VD is zero, the army breaks.  Individual commands can break as well.   The VD has to be calculated for each command.  When one command breaks, all of those units count as breaks for the whole army.  So, it is possible for an army to break before an individual command breaks.  It is also possible that 1 command breaking will break the whole army.

Under the Hood

On the surface, the game is pretty simple.  You roll dice, count the hits and apply them to a cohesion test.  There are also some things that alter the game so that it becomes fairly chaotic.  For instance, when you roll for initiative, you must move the command you chose whether you want to or not.  You might win all of the initiatives for the turn leaving your opponent with the opportunity to move his commands in any sequence he chooses.  Depending on how well you moved during your turn, this may leave you with a long and horrifying wait as your opponent picks your army apart.

Dispirit combat values are not as bad as they seem.  With a little luck, a VBU 2 unit can possibly win a melee with a VBU 6 unit.  I wrote a probability calculator using Troll Roller.  The average hits for VBU 2-6 are as follows:

VBU 2 Hits .36,  VBU 3 Hits .57,  VBU 4 Hits .79,  VBU 5 Hits 1.03,  VBU 6 Hits 1.27

It would not be too unusual to see a VBU 6 unit miss and see a VBU 4 unit score at least 1 hit.

Another aspect of the game is the higher attention to detail paid to the missile combat system.  There are several long bows, composite bows, self bows, a sling, a javelin, 2 crossbows and 3 types of artillery.  Considering that the melee combat system contains little in the way of weapon detail, I found this a bit surprising.  I would have thought that 1 bow and a long/composite bow category would be enough for bow.  The differences in types is usually 1 die and often only at certain ranges.  Simplifying the list of missile weapons would not change things up that much and would fall in line with the simplicity of the melee combat weapons.

I felt the reaction system did not really add much to the game.  It seemed a bit complicated and fiddly for what it was trying to accomplish.  The games played fine without it.  I think I actually used it once.  As the movement rules are pretty restrictive, I don’t even think special ZOC rules are required.  I would be simpler to allow a counter charge by a unit that is in good order and it passes a discipline test.  Similarly, I think it would be OK for a missile unit to shoot if it was charged by an enemy, but only if it were in good order and it passed a discipline test.

Roman line relief was the one historical rule that I had a problem with in the game.  The rules require that you make 2 cohesion tests, one for each unit trying to interchange.  With that, there is a fairly low probability of actually performing the maneuver.  Long handing 2 average units trying to swap spaces would be 50% X 50% or a 25% chance to actually perform the maneuver.  Seems low for something that was a main feature in the Roman army’s success during the time of the Republic.  I would just allow it to happen if the back unit is in good order and the front unit is not engaged or is retreating from a lost melee.

Finally, I’d like to talk a moment about the organization and editing of the rules.  Some folks felt that the rules were hard to understand.  After reading through, I could see why.  The rules set is a translation from Italian.  The wording, while correct through out, could seem a bit awkward and occasionally hard to understand.  With two English language proof readers, the quality of the translation should have been better.  The organization of the book could have also been better.  For the most part, it flowed relatively well.   However, with regard to zones of control and reaction/opportunity, the rules were spread out to several sections.  There were several other minor instances of rules that I had trouble finding.  The book could have done with an index to alleviate the problems.

I played 3 games of Impetus with 2 commands per side.  My first game was Greeks vs Persians at Marathon.  For this battle, no rules changes were needed.  The Persians fought two units deep with the archers in the rear and mixed units in the front.  They were able to inflict some loses on the advancing Athenians but for the most part, the game held up to history.  The armored hoplites closed and made short work of the Persian infantry before the cavalry could join the fight.

The second game pitted a Pyhrric army vs the might of Rome.  This one went down to the wire.  The consular army advanced to contact and started a shoving match with the more numerous and deeper deployed pikes.  At first the Romans were getting the worst of it but started to grind down the pikes and were only just broken with a charge from the rear by the Pyrrhic Agema cavalry and the elephants.

The third fight was Carthage vs Rome.  It was similar to Zama but I simply made 2 armies and added a few Numidians to Rome.  The Carthaginians lined up in three lines and kept the cavalry on the flanks.  Romans were in two lines.   Both armies used skirmishers to the front.  The battle started with the Romans besting the first punic line after a brief struggle.  The carthaginian Numidians bested the Roman Numidians but the Roman cavalry locked in a struggle with the Punic cavalry which lasted most of the game.  After blending through the second punic line, the Punic veterans of the third line proved too much for the worn Romans.  The fight was over.

In all three fights, no rules modifications were needed.  They played well.  I especially liked the way that the large units could be ground down by a superior unit after the initial contact.  The accumulated disorder rule was great at representing this.  Units would get disordered but stay stuck in, thus not being able to rally/reform.  Missile fire could seem a little powerful.  Some weaker units that take a hit could leave the field if they rolled a 6 for cohesion.  Occasionally, the cohesion rolls could get a bit dicey.  On one occasion, I rolled four 6’s for hits and then rolled a 1 for the cohesion test.  No effect.  I liken this to the old Squad Leader morale check.  You roll very low and get a morale check +4 on the enemy. Then the enemy rolls 2 for the test and barely passes.  The number of hit are not casualties but rather the psychological effect on that unit of losses during combat.

I played several games of Basic Impetus as well.  It is, indeed, a ‘lite’ version of the full game.  The games were over in under an hour.  They did have the feel of the era in a basic way.  I played my last game of Basic Impetus with a few rules from Impetus, including my modified reaction rules and the evade rules for skirmishers.  It gave a fun little game with a relatively low figure and unit count.

The support of the game from Dadi & Piombo is quite good.  There is a forum on the website as well as a Yahoo Group.  The author is active at both sites answering questions about the game.


The game plays well and is a nice and (mostly) uncomplicated treatment of Ancient warfare.   Once I got rolling, I enjoyed the game a lot.  Despite the difficulties, I think that the full version of Impetus is worth the money. The game comes in two versions.  The first is Basic Impetus.  It is free from the authors website and includes a large amount of army lists.  It will give you a good idea of how the combat system works.  It’s free so you have nothing to lose.  The second version is that which is reviewed here.  The cost is about $42 in the US and can be ordered from your favorite hobby retailer.

Basic Impetus


Both by Lorenzo Sartori and published by Dadi & Piombo

Price $42