The Tactical, Numerical, Deterministic Model
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The Dupuy Institute believes that the Tactical, Numerical, Deterministic Model (TNDM) is able to forecast what is likely to occur in combat at least as well as any other combat model in use today.


The Tactical Numerical Deterministic Model (TNDM) is an empirically based combat model with a database derived from historical research. It was developed by Colonel Trevor N. Dupuy, (USA, Ret.), from his concept, the Quantified Judgement Method of Analysis (QJMA), as presented in his two books, Numbers, Predictions and War (1979) and Understanding War: History and Theory of Combat (1987). The QJMA has two elements:

  1. Determination of quantified combat outcome trends based upon modern historical combat experience in more than 200 examples of 20th Century combat, mostly World War II and the 1967 and 1973 Arab-Israeli Wars, and
  2. Extrapolation of historical trends to contemporary and future combat on the basis of developments and changes in firepower and mobility technology.

In developing the TNDM as a refinement of an earlier model based upon the QJMA, Col. Dupuy had the collaborative assistance of Dr. James G. Taylor (noted author of works concerning modern Lanchester-type models) in developing a new differential equation attrition methodology based on historical data. By a mathematical process akin to that of the Lanchester Equations, the TNDM attrition methodology provides results consistent with those which occurred in historical engagements. By being historically based, the methodology is more scientifically justified than any methodology not consistent with historical experience.


The TNDM is a quick-reaction, inexpensive, computer-assisted mathematical simulation of air-land combat. It is suitable for planning, for analysis, and for examining a variety of combat situations, ranging from a small-unit, low-intensity combat action, to multi-day corps or army conventional battles.

The TNDM title is descriptive: It is a tactical battle model, although it can be used for planning and analyses of both historical and strategic campaigns. It is numerical; quantified inputs lead mathematically to quantified outputs. It is deterministic; any given set of inputs will always yield the same outputs. (It may be argued whether combat is essentially deterministic or stochastic, but a forecast must be deterministic, whether arrived at by a stochastic or deterministic process.)

The TNDM, designed for use on an IBM-compatible personal computer, is programmed in TURBO-PASCAL. It has been tested extensively in the United States and abroad. It has been modularly designed and can easily implemented with the architecture of existing time-step and event-driven combat simulations. The software allows the historically-validated TNDM attrition methodology to be extrapolated to small unit force-on-force dynamic situations in low-intensity and conventional combat. It can be applied to a variety of different analysis requirements, and as a combat "underlay" for designing and/or evaluating new combat systems/technologies.


Planning and Analysis. Before the outbreak of the Kuwait or Gulf War, in January, 1991, planning analyses using the TNDM forecast casualty rates for US forces far lower than published predictions by any other model. In post-war assessments, adjustment of inputs to those actually experienced in the four-day ground war, yielded TNDM attrition results within 5% of the actual historical experience of US ground forces during the period February 24-28, 1991.

There are two principal reasons for this. The patterns of TNDM attrition and advance rates in replication of historical combat closely correlate to those of historical experience over six decades, during which weapons and mobility technologies underwent sweeping changes. A leading model in use by one of the military services cannot come close to matching the historical patterns. Furthermore, it is demonstrable that suppression effects of weapons on the battlefield are more important in battle outcomes than are attrition effects. Other than the TNDM, no model in use today in the United States or Europe even attempts to represent suppression.

Instruction. The TNDM can closely replicate the results of historical battles. Thus in historical and tactical instruction, it can be used to demonstrate the results of "what ifs?", possible alternative outcomes if changes are made in basic inputs or in tactical decisions.

Purchasing the Right to Use the TNDM

The TNDM is marketed by The Dupuy Institute, a tax-exempt, non-profit corporation established in 1992, dedicated to scholarly research and objective analysis of historical data.

Purchase of the right to use the Tactical Numerical Deterministic Model (TNDM) is available through The Dupuy Institute (TDI). At this time, TNDM version 2.04 (dated 20 January 1998) is offered. TDI is currently working on version 2.05. The entire package consists of:

1. The TNDM Program. This is on 3 1/2 inch diskettes which contain the latest tested version of the TNDM Program. The TNDM diskettes are configured for any IBM compatible personal computer with 286 processing chip or better. This includes the following subroutines: 1. A listing of OLIs for standard weapons of all nations; 2. A calculation program for OLIs.

2. Tactical Numerical Deterministic Model (TNDM): A General Theoretical Description and Hardware and Software Requirements dated October 1994, two copies.

3. Tactical Numerical Deterministic Model (TNDM) Manual of Rules and Procedures dataed October 1994, two copies.

4. Tactical Numerical Deterministic Model (TNDM) User's Guide dated October 1994, two copies. This provides entry-by-entry instructions for using the TNDM Program diskettes.

5. Two copies of all slides used in the TNDM Instruction Course.

6. One copy of all back issues of the International TNDM Newsletter.

We will also provide as part of this contract:

1. The TNDM Familiarization Course.. This is a basic instruction course to be provided by TDI immediately after installation of the TNDM Program at the purchaser's facility.

2. The Annual Maintenance and Support Package. The Dupuy Institute will provide the following support over the course of a year:

  1. Four weeks of technical support on an on-call basis;
  2. One week of training, either familiarization or on selected topics of the customer's choice;
  3. Rapid response service on all technical and analysis problems;
  4. Copies of all software updates as improvements are made to the model;
  5. Periodic status reports on TDI database work, studies and proposed TNDM revisions.

The annual support package is priced at $18,000 per year, excluding travel costs. All travel expenses, including per diem costs, incurred in the performance of work under this package will be paid for by the purchaser.

The price of the rights to use the TNDM, including a one year support package is $138,000. For further information, contact TDI.