Battle of Ad Decimum

One of my friends who knows a lot more about ancient/medieval combat than I do said he wanted to run the Battle of Ad Decimum between the Byzantines and the Vandals, so I did a little research and tried to work it up. In case anyone else is interested in such a thing (or in offering suggestions to make the armies more accurate), here’s the order of battle:

I think we’re going to require a special morale check for Gelimer if his brother dies, and if he fails he’ll lose half of his AP for a few turns, since that’s basically what happened in the real battle.

Sounds like it’ll be fun.

I always forget how small medieval battles were compared to Hellenistic/Roman ones.

The current setup looks like the Vandals are going down hard, even without special rulings.

As I understand it, the Vandals were poorly armed and armored, but all mounted, so make their force 11 units of light cavalry C. I would drop the Byzantine light cavalry entirely, and turn the 1,000 allied horse archers into 1 unit of horse archers, the 2,000-2,500 normal Byzantine cavalry into 2 units of cataphract cavalry, and 1,500-2,000 bucellarios into 2 unit of veteran cataphract cavalry. If it matters, the longbowmen would be of type B rather than type A, lighter armor, but with sheilds. For extra historical accuracy I would drop the Cataphract cavalry’s AC down from plate+shield to chain+shield, as there were probably no Clibanarii employed against the Vandals. All of these adjustments give you a Vandal force that is 86% as strong as the Byzantine Force, which seems both historical and engaging for both players, as the course of battle could easily see either side win. I would not introduce a house rule of further Vandal weakness, as the lack of either heavy horse or damage absorbing infantry should be weakness enough.

The only caveats on this is that I am assuming that A: the armies of 533 AD are fairly similar to the armies of the begining of the 7th century (probable since contact with the Avars has already been made), and B: that Belasarius’ army is sufficiently provisioned to have all his soldiers properly equiped (somewhat probable as it is the main field army of the time). Hopefully 10,000,000 GP (~100,000 lb gold) would buy you an army with all the bells and whistles.

Thanks for the help! Because I really don’t know much about this, I’m just trying to piece it all together. Where did you read that the Vandals were all mounted? I got my numbers of cavalry vs. foot from The Art of Battle. He claims 10K cavalry, 5K infantry for the Byzantines and 7K infantry, 4k cavalry for the Vandals I haven’t been able to check his sources yet, but I plan to pick them up from my library today.

I’m also thinking of doing it as three separate skirmishes; the Ammatas vs. John holding action, the Gibamund vs. Huns, and then the main battle with forces dependent on what happens there.

The only description of a Vandal army in this period comes from Procopius. In History of the Wars, Book 3, Chapter 8, lines 25-29 a Vandal army is defeated by a Moorish army due to lacking infantry and skill with ranged weapons. Since Procopius doesn’t describe the Vandal army at Ad Decimum in detail, we can only assume that its composition was similar.

While I haven’t read either of the sources from The Art of Battle, the description in the video seems to differ widely from all the other descriptions of the battle that I have seen. Procopius’ account describes the Byzantine Infantry as holed up in camp, not struggling to get organized.

While you could divide it up into 3 skirmishes, it might be interesting to play around with the initial army setup to achieve a similar effect. If you take the Ambush layout from page 36 and slide the map over, so that there is no left wing or flank. Ammantas could be the Ambushing Army Rear Guard and John the Ambushed Army Vanguard. Gibamund would probably be pretty deep in the right wing and the Huns could be placed between the Ambushed Main Body and Gibamund. Then you put the main Byzantine cavalry in the Ambushed Main Body and the Infantry in the Ambushed Rearguard. Then Gelimer can be either in the Ambushing Army Right Flank or in the Ambushing Army Right Wing, well away from the Huns and Gibamund. Then you could see if the Ammantas v. John and Gibamund v. Huns skirmishes have time to resolve before Gilemer’s or Belisarius’ main forces can get there.

Roy Boss’ “Justinian’s Wars: Belisarius, Narses, and the Reconquest of the West” gives the OB at Ad Decimum as ** approximately **:

1100 bucellarii (extra armor, lance, bow, buckler)
2800 foederatii (armor, spear, shield)
2000 Roman cavalry (armor, bow)
600 Huns (armor, lance, bow, buckler)
400 Heruls (medium armor, spear, shield)
10,000 regular infantry (half armored spearmen, half unarmored bowmen)


11,000 cavalry (8,000 armored, 3,000 unarmored)

His footnote refers to the main text for details and color, but I don’t see much there, or a direct citation of which sources he pulled this from.

So, we’ll have to try it again to see if it goes the same way, but running it this way (updated order of battle at the original link) led to an overwhelming Vandal victory. Gibamund took out the allied horse archers on the first turn. John fared a little better in the vanguard, but Amatas still pushed him back to the main force pretty easily. From there, it was trying to wheel the main body around to face Gelimer’s force coming in from the side, and just getting pounded by charages over and over.

Not sure the extent to which this was just my tactical shortcomings (I played the Byzantines) and the extent to which we were simulating what would have happened if the Vandals had actually managed a coordinated ambush.

Another thing I didn’t realize until we were setting up is that even though Belisarius has the greater numbers, because cavalry units have half as many people, the unit count was actually 11-10 to Gelimer.