Clash of Empires: Caesar against the Celts The Battle of Bibracte July 58 BC

In this article I’m going to use the Clash Battle System to recreate the Battle of Bibracte (58 BC), which was the second major battle of the Gallic Wars 58 – 51 BC. This battle is significant because it illustrates the relentless form of attack of a Roman Legion as represented by the linear exchange of tired engaged troops for fresh men from the rear ranks. This together with the keeping back of a tactical reserve and good leadership enabled the Roman army to consistently defeat vastly larger barbarian armies.

Background

The opening events of the Gallic War took place in the spring of 58 BC in the Roman province of Transalpine Gaul over which Gaius Julius Caesar had just been made proconsul. Probably for personal aggrandizement rather than any real threat Caesar decided to intercept a migratory horde of Gallic peoples the Helvetti and their allies who were heading for the Rhone Valley in southern Gaul. After winning himself time by feigned negotiation Caesar destroyed the one bridge across the Rhone River and fortified the southern bank. Finding their way blocked the Helvetti decided to take an alternative route through the Jura mountains. By the time they had crossed this barrier Caesar had assembled six legions to block their way. A forced march and surprise attack by three of these legions annihilated an advance group of 30,000 Helvetian warriors as they were in the process of crossing the Arar River. After this clash Caesar positioned his army on a plateau (Mount Beuvary) with four of his more experienced legions in three lines on the slopes and his two less experienced legions and auxiliaries entrenched on the summit. The Helvetti and their allies still had about 70,000 warriors and early on a July afternoon they made their attack against the Romans’ elevated position. The Helvetti surged up the slope in a deep mass, but despite the ferocity of their charge they were unable to prevail against the Roman battle tactics. Gradually they were forced back by the Roman legionaries who due to their training and discipline were able to exchange their front ranks for fresh troops from the rear. At this point the armies of the Boii and the Tulingi who were the allies of the Helvetti attacked the Roman right flank. Thereupon Caesar ordered the first and second lines to keep up the pressure on the Helvetti while he detached the third line which was in reserve and turned it to face the new threat. By the end of the day the Gallic warriors had had enough and after a last stand in their camp they were slaughtered. In the violent struggle 130,000 Helvetians including women and children fell. Roman losses were heavy but not known precisely.

Clash of Empires

Using the Clash of Empires rules the battle strength and capabilities of the belligerents can be shown as follows: -

Later Republican Roman

Standing Army type (following the reforms of Caius Marius) CR ❸, which based upon the number of army units i.e., 27 converts to a +21 Fighting Bonus (FB). A Standing Army also get +1 to Initiative for Forced March. Battle Dice 2D6 (highest scoring die only). Fighting Technique: Legion which gives the Romans a +2/+4 modifier to their Battle Dice score for Heavy Infantry. The second modifier is used if FB greater than that of the opponent. Also, a Standing Roman Legion can save against defeat by rolling 4-6 on 1D6 which is owing to their Special Ability Relentless. If successful, the Roman army can fight again. In this refight any tactical or numerical superiority that either side might have is negated. If the Romans choose not to refight then they can disengage with 25% losses to the loser and 10% losses to the winner. The Romans also have Heavy Cavalry which gives them a 1D6+2 Advantage Die as well as the normal +1 to Initiative for cavalry. At this early stage in his military career Caesar is ranked as competent and rolls 1D6 for Initiative. Therefore, the Later Republican Roman army rolls 1D6 +2 for Initiative. The Roman army is significantly outnumbered by its opponent.

Gallic Army

Warband Army type CR ❶, which based upon the number of army units i.e., 56 converts to a +17 Fighting Bonus (FB). Battle Dice 2D6 (highest scoring die only). Fighting Technique: Battle Rush which gives the Gallic army a +3/+6 modifier to their Battle Dice score for a ferocious charge. The second modifier is used on an Initiative win. In addition, the Gauls have Medium Cavalry which gives them a 1D6+1 Battle Advantage Die as well as the normal +1 to Initiative for cavalry. The leader of the Gallic host is Divico and he is a competent commander who rolls 1D6 for Initiative. Therefore, the Gallic army rolls 1D6 +1 for Initiative and outnumbers its opponent by more than 2-1 so gets 2D6 Battle Advantage Dice.  

Clash Battle System

After rolling for Initiative the Battle Roll for each army consists of the following procedure:

• Roll Battle Dice (highest scoring die only)

• Plus, Combat Rating (CR) to Fighting Bonus (FB) (conversion dependent upon number of units)

• Plus, Battle Bonus calculation determined by the army type and FB.

• Plus, Advantage Dice (representing a numerical, tactical or other special advantage)

Highest score wins and the difference between the two Battle Rolls determines the number of casualties.

Combat Rating to Fighting Bonus Conversion and Casualty Tables not shown.

Battle Log

Later Republican Roman

Initiative	Battle Dice (Modifiers)	CR to Fighting Bonus	Battle Bonus	Battle Advantage Dice	Total Score
1D6 +2 4+2 = 6	2D6 Legion (+2/+4) 5 and 4 (Highest die only) 5+4 = 9	❸x 27 = +21 FB Relentless 4-6 Saving roll = 4	No odds or evens 3D6 3+3+1 = 7	Tactical Advantage 1D6 Heavy Cavalry 1D6+2  3+(1+2) = 6	9+21+7+6 = 43
Refight	2D6 (+4) 6 and 4 6+4 = 10	+21 FB	Evens Dice  4D6 5+5+4+1  = 15	Heavy Cavalry 1D6+2 6+2 = 8	10+21+15+8 = 54

Gallic Army

Initiative	Battle Dice (Modifiers)	CR to Fighting Bonus	Battle Bonus	Battle Advantage Dice	Total Score
1D6 +1 4+1 = 5	2D6 Battle Rush (+3/+6) 5 and 5 (Highest die only) 5+3 = 8	❶x 56 = +17 FB	Odds Dice 2D6 6+5 = 11	Opponent outnumbered more than 2-1 2D6 Medium Cavalry 1D6+1  6+5+(4+1) = 16	8+17+11+16 = 52
Refight	2D6 (+3) 2 and 3 3+3 = 6	+17 FB	No odds or evens 1D6 = 5	Opponent outnumbered more than 2-1 2D6 Medium Cavalry 1D6+1 5+3+1(+1) = 10	6+17+5+10 = 38

Battle Bonus Calculation Table

FB	Warband	Feudal	Citizen	Part-Standing	Standing
1-4	1D3(1D6)	1D3(1D6)	1D3(1D6)	1D3(1D6)	1D6(2D6)
5-8	1D3(1D6)	1D3(1D6)	1D3(1D6)	1D6(2D6)	1D6(2D6)
9-12	1D3(1D6)	1D3(1D6)	1D6(2D6)	1D6(2D6)	2D6(3D6)
13-16	1D3(1D6)	1D6(2D6)	1D6(2D6)	2D6(3D6)	2D6(3D6)
17-20	1D6(2D6)	1D6(2D6)	2D6(3D6)	2D6(3D6)	3D6(4D6)
21-24	1D6(2D6)	2D6(3D6)	2D6(3D6)	3D6(4D6)	3D6(4D6)
25+	2D6(3D6)	2D6(3D6)	3D6(4D6)	3D6(4D6)	4D6(5D6)

(#D#) = Enhanced Battle Bonus on odds or evens Battle Dice.

Note: - The Roman army manages to win Initiative and takes up a position on high ground in three battle lines. The enemy clash violently with the first line and due to the ferocity of their attack illustrated by their Enhanced Battle Bonus and numerical superiority would have won the battle had not the Romans successfully made their Relentless saving roll. This represents the first line when hard pressed falling back to be relieved by the second line and the deployment of the reserve to counter the Gallic flank attack. On the refight roll the Romans score 54. Thus, they win a decisive victory for the loss of 6 units, whereas the Gallic army is destroyed.

Caesar’s legions clash with a migratory Gallic horde at Bibracte 58 BC. Figures by Essex and Irregular Miniatures from their 25mm Ancients range. Painted by Silurian and from the author’s own collection. The numerical strength of each army is denoted by the coloured plastic counters. Game board from the Clash of Empires: The Hellenistic World Game.

The imposing Gallic horde crashes into the first line of the Roman army at the Battle of Bibracte 58 BC. Figures by Essex Miniatures from their 15mm Ancients range. Painted by Silurian and from the authors own collection. Army composition calculated by the Clash Conversion Table for Wargaming.

Sources

Boulter, M. L. 2009/2025: Clash of Empires: The Hellenistic World. Silurian War Games Ltd.

Dupuy, R. E. and Dupuy, T. N. 1993: The Collins Encyclopaedia of Military History. Harper Collins Publishers.

Hackett, J. 1989: Warfare in the Ancient World. Sidgwick & Jackson Ltd.

Jimẻnez, R. L. 1996: Caesar Against The Celts. Spellmount Limited.

Mellersh, H.E.L. 1995: Chronology of the Ancient World, 10,000 BC – AD 799. Helicon Publishing Ltd.

Article Front Page Picture

Vercingetorix throws down his arms at the feet of Julius Caesar. Museum: Musèe Crozatier, Le Puy en Velay. Author: Royer, Lionel. Roman Legion. After Alamy (IY04575193).