Assuming you don't know what miniatures wargaming is:
DBM (De Bellis Multitudinis) is a game played with little metal or plastic soldiers on a tabletop covered with model scenery. The soldiers are chosen to represent historical armies from anywhere from the age of the Egyptian Pharaohs to the beginning of Europe's Renaissance. People will build and paint armies of about 40 - 100 pieces, each piece called an element and having two to eight model soldiers on it who may be infantry or on horses, camels, elephants, chariots, manning catapults, etc.
There are rules regarding such things as how far different kinds of elements like knights or pikemen move each turn, how ambushes work, when an army collapses from losses and other aspects of ancient battle. Dice are used to regulate how many moves each player gets to make each turn, simulating a general's limited ability to command and control his troops, and for resolving fights between troops that can shoot each other or fight in hand to hand combat. A game represents one battle. The battle can be historical, historically possible, or an impossible matchup between armies separated by time or space. It takes about 2 to 5 hours to play and is typically played by 2 to 6 people.
The initial outlay to play is about $13 for the rules and $13 for your first army list book that contains a bunch a army descriptions for a historical era. A bit less if you can buy it in or order it from England. After that, you can begin with cardboard markers that you make to fit the element sizes described in the rules and if you like the game, buy and paint your first army of soldiers to replace the cardboard pieces. The bare unpainted metal soldiers for the most common scale (about 15mm tall) will cost $50-$75 in the U.S. Some people paint and sell finished armies. These tend to run about $250-$400 for nicely done 15mm armies but you may find a bargain or less nicely painted figures at a wargame convention. There are people playing the game in most English speaking countries and in several other countries like France, Spain, Italy, Sweden, Finland, Germany, etc. both informally in their homes and in tournaments organized by local, national, and international groups.
The company that publishes DBM is named Wargames Research Group and is in England. They have been the dominant publisher of miniatures rules for ancient era wargames since the 70s. Their games went through six editions with various tweaking, a 7th edition that was quite a departure, DBA which is a very simplified smaller game, and DBM which is a cross between 7th edition and DBA. There are popular competing sets of rules from Arty Conliffe - Tactica and Armati, known for being easier to read than WRG ancients rules, but while they have some ardent adherents, more people still prefer WRG 7th or DBM, and a variety of other rules sets from other publishers for playing battles in the ancient era and middle ages. The nice thing about gaming with miniatures is once you have painted some troops, trying a new rules set is a relatively small investment.
If you already know what miniatures wargaming is:
DBM is WRG's new (when this article was first written in 94) system for ancient battles, a successful hybrid of WRG 7th and DBA mechanics. It is presently in version 1.1, dated June 1994. It consists of a rules booklet that costs about $14 in the U.S. and four army list booklets at about $13 each (see the FAQ for info on ordering directly from The Keep at a somewhat lower price).
Book 1 is the Biblical era. Book 2 is from approximately 400 BC to 500 AD. Book 3 is from approximately 500 AD to 1000 AD. Book 4 is from approximately 1000 AD to 1500 AD.
The rules are fast playing and very clear when compared to other rules by Phil Barker, due largely to the efforts of co-author Richard Bodley Scott, but still somewhat hard to read compared to, say, Arty Conliffe's style of rules writing. They have a few holes and gray areas, endlessly teased apart on the DBM mailing list, but play very smoothely in actual practice, causing few arguments in club or tournament play.
The figure basing is the "WRG standard", 40mm wide for 15mm troops, 60mm wide for 25mm troops, with 2 to 4 figures and depth varying with the number and type figures on a base, usually 15, 20 or 30mm for 15mm troops. One base is called an element and is the basic maneuver unit in the game. An element nominally represents 125 to 250 men. An army will typically have from 40 to 100 elements, depending on quality and cost of each element and the number of points each side is alloted to buy troops from their army list.
More people play DBM in 15mm than in 25mm. The usual playing area for a 15mm game is 6 feet by 4 feet.
Measurements are usually done in paces, with 50 paces to the inch in 15mm scale. Often distances are specified in element depths or element widths in specific rules. For instance the distance at which an element can prevent an enemy from crossing its front is one element width, and most troops who lose a fight but not badly recoil the depth of their element.
Troop types are simpler than in WRG 7th, each element being rated as irregular or regular, by type like spears or knights ala DBA, and by quality, like (S) for superior, (O) for ordinary, (I) for inferior, or (F) for fast. The ratings bear on combat proficiency versus specific foes, PIP costs, movement distances and restrictions, terrain effects on the element, impetuous behavior, and the point cost of the element.
Command and control is handled by dividing an army into 2 to 4 commands, each one under a general. One of these is the CinC's command. A PIP die is thrown for each command and the score is the number of moves that may be made in the turn by individual elements or groups of adjacent elements facing the same direction. Certain actions require more than one PIP and the table that defines what costs how many PIPS bears re-reading and consulting frequently while moving for your first few games. For example, most irregulars cost an extra PIP to move in any direction but straight ahead, and also cost PIPs to hold in place, unlike DBA. The CinC's command make make one move or hold that includes the CinC element at one PIP less than normal, usually a free move, or a bunch of knights or warbands attached to the CinC being held steady for only 1 PIP. Each command thus operates nearly like a DBA army, except that there are more ways that a move will cost extra (or occasionally fewer) PIPs. Also the concept of March moves comes in from WRG 7, in which an element or group can spend more PIPs to make additional moves in the same turn until it gets close to the enemy (within 200 paces). This allows one to possibly advance a command boldly to pin an enemy wing, rapidly move a reserve to a threatened area, or similar moves that control the tempo of the game and where the fighting occurs, much more than you can do in DBA. At first a well-dpeloyed army can move reasonably well even on low PIP scores, but as groups get disrupted by maneuvering or combat, you wind up doing more and more single element or small group moves trying to meet the most desperate threats. It is quite possible to "fight the enemy's PIP dice" by using stratagems that break up his formations or require himt o use up lots of PIPS to redeploy or reorient forces, while you hopefully are making more efficient use of your own PIPs to force decisive advantageous combats.
Impetuous movement, flank marches entering from the sides of the table when the PIP dice are right and ambushes in covering terrain on table are other parts inherited from WRG 7 that bring more flexibility than DBA has.
Combat basically follows the DBA model with some changes inthe factors and results tables and additional subtleties from the finer gradation of troop types. Basically combat is conducted by element pairs lined up across the fighting front, with each troop type adding a characteristic number to a D6 roll, modified by various tactical factors. Each of the two opposing elements has a die rolled for it and the higher score wins. Ties are locked in combat except for some rare exceptions. Usually the loser recoils its depth if it is beaten or destroyed if doubled. Some troops types will destroy particular opponents by simply beating them. Some will flee (possibly to return) instead of being destroyed when doubled. Elements that don't have room to recoil because friends behind them are facing in other directions or enemey are behind die instead. Elements that are killed in close combat sweep away friends within an element depth behind them in the panic. Impetuous winners have to follow up their depth but other winners stand their ground. Superior troops are harder to recoil and kill and inferior troops crumble quickly.
A command becomes demoralized when 1/3 of its elements are killed or if the general is killed and the next PIP score is less than or equal to the number of elements lost by the command at that time. Then the demoralized elements begin to flee, though some can sometimes still be held or used usefully with good PIP dice. All opposing elements nearer to demoralized enemies than undemoralized enemies become impetuous, which can often be very hazardous to the victors, as they are often rather broken up form their original formations by the combat.
Victory is determined by demoralizing or destroying half of the opponent's army before he does the same to you.
I really like DBM. It gives an ancient or medieval battle that can be completed in a reasonable amount of time, using troops that mostly work the way you would expect their historical counterparts to, without dwelling on the minutiae of armaments too much. It gives a lot of opportunities to win by generalship and yet you can lose to the fate of the dice sometimes even if your plans are better. It is a comfortable step up from DBA and works well for one on one or multiplayer games. It has superceded WRG 7th for many old grognards and DBA for many ancients novices who started recently. Veterans of WRG 7th seem to be of the opinion that the army lists are better balanced to each other with fewer "loser" or "killer" armies. It has inspired me to paint a lot more ancients lead than I would have otherwise.
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Ed Allen
allen@sequence.stanford.edu DBM mailing list keeper