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This field manual (FM) is part of the FM 100-60 series that documents the capabilities-based Opposing Force (OPFOR). This series provides a flexible OPFOR package that users can tailor to represent a wide range of potential threat capabilities and organizations. The overall package features an armor- and mechanized-based OPFOR module and an infantry-based OPFOR module. Each module contains field manuals that describe organizations, operations, and tactics. A third module describes the organizations, operations, and tactics of other OPFORs not covered in the first two modules. A separate field manual provides characteristics of worldwide military equipment available to the capabilities-based OPFOR organizations in the three modules.

This introduction provides definitions of some basic terms used throughout the manual. For definitions of other key terms, the reader should refer to the index, where page numbers in bold type indicate the main entry for a particular topic. The referenced page often includes a definition of the indexed term.


The OPFOR is a training tool for preparing the Army to respond to a variety of threats. The following paragraphs explain the difference between an OPFOR and a threat and the relationships between the two.

Threat and Country-Based OPFOR

In simplest terms, a threat is a potential adversary. It can be any specific foreign nation or organization with intentions and military capabilities that suggest it could become an adversary or challenge the national security interests of the United States or its allies. As the Army moves into the twenty-first century, it is no longer possible to identify one or two nations or forces as the potential adversaries against which it needs to train on a regular basis.

When conflict is imminent, or when U.S. forces need to train for a particular contingency, training may focus on a specified threat force. This rehearsal for an actual mission or operation can involve a country-based OPFOR. Such an OPFOR should portray the specified, real-world threat force with the greatest possible fidelity based on the best available classified and unclassified information. Cases may exist in which constraints on the use of classified information preclude the use of actual threat data. Sometimes certain threat information may not be available at any level of classification. In such cases, trainers could fill in gaps by using those parts of the capabilities-based OPFOR that are most consistent with what they do know about a specific threat.

Capabilities-Based OPFOR

In more typical cases, however, the U.S. Army simply needs to train against an OPFOR that represents a particular level of capability rather than a particular country.1 The capabilities-based OPFOR is a realistic and flexible armed force representing a composite of varying capabilities of actual worldwide forces. It constitutes a baseline for training or developing U.S. forces in lieu of a specific threat force. This baseline includes doctrine, tactics, organization, and equipment. It provides a challenging, uncooperative sparring partner representative, but not predictive, of actual threats.

Spectrum of worldwide military capabilities.

The capabilities-based OPFOR represents a break from past practices in two principal respects. First, the armor- and mechanized-based and infantry-based OPFOR modules are not simply unclassified handbooks on the armed forces of a particular nation. Rather, each module has its basis in the doctrine and organization of various foreign armies. These OPFOR modules are composites deliberately constructed to provide a wide range of capabilities. Secondly, the modules do not provide a fixed order of battle. Rather, they provide the building blocks from which users can derive an infinite number of potential orders of battle, depending on their training requirements.

The primary purpose of the field manuals in the 100-60 series is to provide the basis for a realistic and versatile OPFOR to meet U.S. military training requirements. They can support training in the field, in classrooms, or in automated simulations. However, users other than trainers also may apply the information in these manuals when they need an unclassified threat force that is not country-specific.


Field Manual 100-60 depicts the forces of a developed country that devotes extensive resources to maintaining a military capability that rivals that of the United States. The name of that country is the State. It can have a strategic capability, with strategic air and air defense forces and strategic missile forces. It probably has a nuclear capability. Unless the State is landlocked, it can have a blue-water navy and naval infantry (marines).

In the armor- and mechanized-based OPFOR, ground forces are the largest component. The formal name of this branch of the armed forces, which corresponds to the U.S. Army, is the Ground Forces. These Ground Forces comprise several standing divisions and separate brigades, most of which are subordinate to standing armies or corps. Most of these forces are, in turn, subordinate to army groups. Army groups, armies, and corps can vary widely in strengths and capabilities. Even multiple army groups may come under a series of theater headquarters that orchestrate complex, large-scale operations.

The armor- and mechanized-based OPFOR can conduct a strategic operation involving the combined forces in a theater. These forces may comprise--

  • Several army groups.
  • Strategic nuclear forces (strategic missile forces and strategic aviation).
  • Strategic air armies.
  • National air defense forces.
  • A naval fleet.
  • Naval infantry forces.
  • Airborne forces.
  • Special-purpose forces.
  • National space forces.

Trainers may use any or all of these elements in an OPFOR order of battle as required.

Armor- and mechanized-based forces are the norm throughout the industrialized world. Such armies normally mount at least 40 percent of their ground forces in armored vehicles. They tend to modernize selected systems to match the best systems deployed by their neighbors. In terms of equipment and size, they range from small forces fielding outmoded equipment to large, capable forces fielding state-of-the-art weapons. For the most part, they base their tactics and doctrine on either their own experience or that of their arms/doctrine suppliers. Many of these nations produce and export weapons and technology up through state-of-the-art systems. If not, they have the financial resources to purchase such systems. Significant technologies that mark this class are in fire support and target acquisition.

Size and Capability

The armor- and mechanized-based OPFOR module includes a range of potential forces that can vary in size and capability. Small-to-medium armor- and mechanized-based forces cover a wide range of technology and capability, from developing states through small, professional armies. Large armor- and mechanized-based forces often have more sophisticated weaponry. Both types can field self-propelled artillery and multiple rocket launchers; artillery-delivered precision munitions; medium-to-heavy tanks; and limited thermal capability. These forces may or may not have nuclear weapons but at least have the capability to produce or acquire them. The more advanced states have the logistics and command structures necessary to conduct continuous operations, and joint operations are the norm. Large armor- and mechanized-based forces can conduct large-scale, combined arms operations. Some such forces are capable of sustained power-projection operations.

The high-technology end of the armor- and mechanized-based OPFOR approaches the level termed complex, adaptive forces. From developed nations, these most technically and tactically advanced forces can choose quality over quantity. As they modernize, they can reduce in size and still maintain a high level of military capability. These forces normally have a complex structure, with more specialized units operating highly sophisticated equipment. They are also capable of adapting to dynamic situations and seizing opportunities on the battlefield. However, such a force is exceedingly expensive to equip, train, and maintain.

Thus, the differences between the infantry-based and armor- and mechanized-based OPFOR modules are largely scenario-dependent. A particular training scenario may not require a large array of standing forces or justify the extensive use of mechanized infantry or tank forces. If not, the infantry-based forces of FM 100-63 may better fit training needs. Sometimes trainers may find it necessary to draw some elements from both organization guides in order to constitute the appropriate OPFOR order of battle.

Compared to Infantry-Based OPFOR

Infantry-based forces are common throughout the developing world. None of these forces is capable of meeting the most advanced armies on an even footing in conventional battle. An infantry-based force differs from an armor- and mechanized-based force primarily in terms of technological level and the ability to integrate arms into combined arms combat.

The infantry-based OPFOR generally represents the armed forces of a developing country with limited resources. The name of that country would also be the State. In this case, the State's military structure still consists primarily of the Ground Forces. However, these Ground Forces are primarily infantry (dismounted or motorized), with relatively few mechanized infantry and tank units and perhaps some airborne infantry units. Compared to the armor- and mechanized-based OPFOR, these forces typically have fewer standing divisions and brigades. However, infantry-based forces, too, can vary in size and capability.

The focus of FM 100-63 is on small-to-medium infantry-based forces in which divisions and separate brigades are subordinate to military regions and districts. They have some armor but rely on dismounted or motorized infantry for the bulk of their combat power. They normally conduct set-piece operations, integrating arms at the tactical level. A small infantry-based force typically has marginal integration capability (ability to conduct tactical-level combat actions with limited fire support) or basic integration capability (ability to conduct battalion-level tactical combined arms actions). Even with a small infantry-based force, however, the State might mobilize and deploy one army- or corps-size force capable of conducting large-scale operations against a neighboring country whose armed forces are also infantry-based. A medium-size infantry-based force may have one or more standing armies or corps and the capability to integrate forces at the lower end of the operational level. In terms of technology, both groups import most of their systems.

Medium and large infantry-based forces may also possess significant armor- and mechanized-based formations. They typically use these heavier units as exploitation forces or mobile reserves. Large infantry-based forces can have multiple armies or corps and conduct extensive set-piece operations over broad frontages. However, they are normally capable of projecting military power only within their region. The key technologies that can allow this are self-propelled artillery and offensive chemical and biological warfare. The State may or may not have chemical and biological weapons, but has the capability to produce or acquire them. A country with large infantry forces can have extensive, basic weapons industries, or it may still import most systems.

When opposed by an adversary of similar capabilities, an infantry-based OPFOR can conduct conventional, force-oriented combat. However, when faced with a large, technologically advanced army, it may choose to redefine the terms of conflict and pursue its aims through terrorism, insurgency, or partisan warfare. In the case of intervention by an external power or coalition, this strategy aims to undermine the enemy's will to continue the conflict without the necessity of defeating his main forces on the battlefield.2

Aside from the Ground Forces, the State's armed forces may include any or all of the following components:

  • The Air Force, including the Air Defense Command.
  • The Special Operations Command, with commando and special-purpose forces.
  • The Navy, consisting of a small, brown-water force.

This OPFOR can also include less-capable forces, such as internal security forces, the militia, and reserves. This menu of possible forces allows U.S. military trainers to tailor the OPFOR order of battle to meet virtually any training requirement involving an infantry-based force.

Field Manual 100-63 depicts infantry-based forces of a country that is divided geographically into an unspecified number of military regions, each with a number of subordinate military districts. This OPFOR stations most combat forces within military districts that can vary widely in their strengths and capabilities. The organization guide allows for standing divisions, but districts with separate brigades would be much more common and in keeping with the spirit of the infantry-based OPFOR concept. If the trainer requires a large infantry-based force, the combined use of FMs 100-60 and 100-63 may better suit his purpose.

Compared to Other OPFORs

Field Manual 100-66 provides a menu of other OPFORs to meet U.S. training objectives in stability and support operations. Compared to either OPFOR module described above, these other OPFORs are less well defined. By their very nature, they are unpredictable. They differ from an armor- and mechanized-based or infantry-based OPFOR primarily in size, technological level, and the ability to integrate arms into operations.

In this case, most military forces have lower capability than an infantry-based OPFOR. These may be the forces of a preindustrial nation or a nonnation group. With limited assets, most such groups cannot, or will not, invest in the weapons and technology necessary to keep pace with the best militaries in their regions. Rather than standing organizations with predictable structures, most of their military organizations are ad hoc. Depending on the situation, these irregular forces may bear the labels of insurgents, guerrillas, or light infantry. There may also be more organized forces such as internal security forces or regular military units. The common thread is that they have little or no organic heavy equipment.

Like the lower end of the infantry-based OPFOR, these forces are likely to attempt to deal with a larger, more technologically advanced army through terrorism or insurgency. They do not try to meet such an enemy head-on in conventional combat. They prefer hit-and-run raids, ambushes, terror tactics, or harassment.3 They try to be unpredictable and invisible, employing methods not anticipated by their enemies. They do not fight by the rules of conventional warfare.

These OPFORs may also include forces that are better equipped and better trained. They may be part of or sponsored by a large-scale drug or criminal organization, or they may have the backing of a wealthy outside power. They may still be small and lightly armed but could have sophisticated, state-of-the-art light weapons. They are light not out of austerity but for practical reasons, because the lightness of the equipment enhances mobility. They may also have high-technology communications and reconnaissance means.

There may be occasions where OPFORs encountered in stability and support operations include a sophisticated military organization with heavier weapons. If the U.S. force is participating in a peacekeeping operation, for example, the OPFOR may be the recognized military of a belligerent nation. As such, it could include armor- and mechanized-based or infantry-based forces of the types found in FMs 100-60 and 100-63, respectively. Likewise, some types of OPFOR described in FM 100-66 can also appear during war.

Like other manuals in this series, FM 100-66 addresses the situation from the OPFOR's perspective. The U.S. force training against the OPFOR may consider itself as performing stability and support operations in an environment of peace or conflict. However, the OPFOR may consider itself at war. Still, the OPFOR concept of victory does not necessarily equate to defeating U.S. forces in a force-on-force battle.


FM 100-61 provides the trainer with a military doctrine and operational art for the armor- and mechanized-based OPFOR. The operational art describes how army groups, armies, and corps conduct operations. The manual also addresses strategic and theater operations, to provide a larger context for the actions of the organizations listed above. Armor- and mechanized-based OPFOR tactics for divisions and below are described in FM 100-62.

How to Use This Manual

To use FM 100-61, trainers must first develop a scenario. This scenario includes a specific order of battle derived from FM 100-60 or a combination of FM 100-60 and FM 100-63. The scenario should also include, among other things: a defined area of operations; significant military, political, and economic information; and a "road to war" events list. The events list drives the conduct and tempo of the scenario. The scenario is subject to approval by the trainers' OPFOR-validating authority. After approval, the OPFOR organization or player uses the operational art described in this manual to "fight" the OPFOR.

FM 100-61 describes a flexible, thinking OPFOR that does not adhere to rigid templates. At the same time, the manual provides parameters for OPFOR actions. Training (BLUFOR) units can. therefore, use this manual to analyze and understand the OPFOR before the battle. In so doing, BLUFOR commanders and staffs must understand that this manual is more than a "rulebook" to limit the OPFOR. FM 100-61 is a training tool that trainers and OPFOR organizations must use with flexibility to meet their training requirements.

OPFOR Symbology

The OPFOR uses a modified form of the military symbology outlined in FM 101-5-1. In this case, the OPFOR units are the friendly forces. The OPFOR depicts its enemy by using double-lined versions of the same symbols it uses for its own (friendly) forces.

1 Another definition of threat is in terms of a capability rather than a country. This could be any advanced technology or system possessed by a militarily significant country, including western or developing countries. The proliferation of such foreign systems or technologies could pose a threat to the U.S. Army or its systems.

2 Throughout the FM 100-60 series, the term enemy refers not to the OPFOR but rather to the enemy of the OPFOR.

3 Although various OPFORs depicted in FM 100-66 may use terror tactics, one specific type of OPFOR is a terrorist group.

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