forces are operating, designated to coordinate fire support, the positioning of forces, or the maneuver of units.

Each ground maneuver unit establishes FLOT and FEBA lines to determine unit deployment. The FLOT encompasses all of the unit's people. Accordingly, the FLOT is likely to extend well beyond the location of the main body of friendly troops to incorporate screening or covering forces. On the other hand, the FEBA depicts the forward limits of the main battle area and specifically excludes the screening or covering force.

In today's doctrinal dialogue, one does not hear much discussion of the FEBA. Interest has shifted to the FLOT. In a 10 August 1981 memorandum to his commanding general, then Brigadier General McDonald Morelli of TRADOC described the Army's rationale for emphasizing the FLOT:

The primary reason the US adopted FLOT in its AirLand Battle operational concepts stemmed from the change in the operational concept and mission of the Corps Covering Force, approved by General Starry several years ago. Essentially, when General Starry decided that the Covering Force would be the first echelon of defense and fight a major battle to force the enemy to deploy his main body, there was no way to depict a FEBA for this "battle area" and remain in consonance with approved NATO terms (NATO definition of FEBA excludes the covering force operations). General Starry decided to use FLOT since the Covering Force Battle was to be the baseline where he wanted the time lines established and the AirLand Battle to begin.4

In brief, today's baseline battlefield control measure is the FLOT.

According to JCS Pub. 1, the planning line most often linked with tactical air operations is the FSCL, defined as:

fire support coordination line (FSCL)—A line established by the appropriate ground commander to insure coordination of fire that is not under his control but may affect current tactical operations. The fire support coordination line is used to coordinate fires of air, ground or sea weapon systems using any type of ammunition against

surface targets. The fire support coordination line should follow well defined terrain features. The establishment of the fire support coordination line must be coordinated with the appropriate tactical air commander and other supporting elements. Supporting elements may attack targets forward of the fire support coordination line without prior coordination with the ground force commander, provided the attack will not produce adverse surface effects on, or to the rear of, the line. Attacks against surface targets behind this line must be coordinated with the appropriate ground force commander."

The FSCL is based on and measured from the FLOT. Ideally, the FSCL should be placed as close to the FLOT as operational and safety considerations permit-say, about ten to fifteen kilometers. For reasons that we shall elaborate later, the FSCL is nearly always found at least twenty-five kilometers from the FLOT when operating with U.S. ground forces.

Historically, the FSCL is the lineal descendant-no pun intended-of the "no bomb line." Before the advent of accurate navigation aids and the current air-ground operations system, easily recognizable terrain features were used to separate the Army and Air Force portions of the battlefield. As one young Army author noted: "Given the problems of communications, coordination, and response time, rigid separation of Army and Air Force fires was the only way to attack targets while protecting our own troops." We should not minimize these difficulties even today, but our focus now is on how to attack the target set jointly, rather than on a battlefield that is hived off into exclusive domains.

While the requirement to coordinate attacks inside the FSCL is clear, there is no JCS Pub. 1 definition of "coordinate." By way of general guidance, JCS Pub. 2, Unified Action Armed Forces, describes the coordination process:

The commander of the supported force [will] indicate in detail to the supporting commander the support missions he wishes to have fulfilled and provide such information as is necessary for complete coordination of the supporting action with the action of his own force.

In other words, coordination during attack

planning seems not to require active involvement of the supporting force when that force is responding to the request of a supported force. Whatever "coordination" is, responsibility for doing it rests mainly with the commander seeking the action. In the case of fire support, the request specifies desired target and time over target. As a consequence, one could argue that the request itself embodies the requesting commander's coordination.

To summarize, we are required to "coordinate" attacks inside the FSCL. The particulars of coordination are not well defined. And in the case of attacks requested by the ground commander, the request itself may be viewed as incorporating the required coordination.

TACAIR Missions

JCS Pub. 1 defines our principal air-toground missions as follows:

close air support-Air action against hostile targets that are in close proximity to friendly forces and that require detailed integration of each air mission with the fire and movement of those forces.

air interdiction-Air operations conducted to destroy, neutralize, or delay the enemy's military potential before it can be brought to bear effectively against friendly forces, at such distance from friendly forces that detailed integration of each air mission with the fire and movement of friendly forces is not required.

Note the absence of any reference to the FSCL. No form of the verb "to coordinate" is mentioned in either definition. As can be seen, what distinguishes close air support from air interdiction is the element of "close proximity," together with its associated requirement for "detailed integration"-not the question of where the mission is conducted relative to the FSCL, with its associated requirement for "coordination."8 (Those who claim that we do only CAS inside the FSCL should advocate changing its name to fire support detailed integration line.)

As with "coordination," there is no agreed

military definition of "detailed integration." In practice, "detailed integration" refers to a comprehensive planning and execution process that extends from target and munitions selection through weapons delivery and incorporates "coordination" as a part of the process. In essence, the ground commander chooses CAS targets, desired munitions effects, and attack timing. A tactical air control party (TACP)-notably the corps air support operations center (ASOC)-does detailed planning to integrate requested attacks with the ground maneuver scheme. Forward air controllers (FACS) communicate with air and ground mission commanders, providing terminal control while weapons delivery is performed.

Adding a final complexity to this vexing question of definitions, "close proximity" has no jointly agreed meaning. From an airman's viewpoint, when the position of friendly troops is known precisely, safety considerations argue for a nominal safe distance to account for delivery system accuracy and frag envelope-say, one to five kilometers. For the Army, "close proximity" is usually associated with the limits of observed fire. The distance at which ground fire can be observed will vary with circumstances, but a good working number is three to five kilometers. Thus, by most accountings, "close proximity" ends at some point well inside the FSCL.

The lack of precision in agreed definitions, especially that of "close proximity," increases the potential for confusion. The situation is certainly clarified if we take the view that, inside the FSCL, we do close air support exclusively and, outside the FSCL, we do air interdiction exclusively. Were this the case, the FSCL would constitute a mission line, rather than simply a coordination line. Indeed, such an arrangement would work well if the FSCL were to be placed in such a way that it could be used as a reasonable guide for "close proximity." However, this is very unlikely to happen, for a variety of reasons:

• The FLOT must remain behind the FSCL

at all times (excluding inserted forces operations). Thus, the FSCL is placed sufficiently distant from the FLOT to accommodate the most optimistic projection of friendly forward movement until the FSCL is again adjusted (normally every twelve hours).

• The administrative process of locating the FSCL, coordinating the position with adjacent commanders and with the appropriate tactical air commander, and disseminating the map trace takes time. This time, and any FLOT movement associated with it, must be allowed for in FSCL placement.

• Standard procedure requires that there be no movement of the FSCL back toward the FLOT in selecting "well-defined terrain features."

• Finally, because we recognize that a mistake can result in friendly casualties, each step in determining final placement of the FSCL includes a margin for error which takes account of, among other factors, friendly unit location uncertainty.

Thus, we almost never see. FSCL placement inside twenty-five kilometers from the FLOT. Thirty to forty kilometers seems to be the U.S. norm, and the distance can be even greater under certain battlefield conditions.

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Accordingly, we cannot expect the FSCL to constitute a reasonable boundary line between close air support and air interdiction. As a consequence, were we to insist on not doing air interdiction inside the FSCL, it would be sible to construct a doctrinal "no-mission zone." In the area between about five kilometers from the FLOT out to the FSCL, we would not do close air support, because targets are not in "close proximity" to friendly forces, and we would not do AI, because the targets are inside the FSCL. There is "no mission" that applies in the zone where attacks must be coordinated but need not be integrated.

FSCL and the Target Array

A major disadvantage of the FSCL as a battlefield control measure is that it bears no direct

relationship to the density or distribution of enemy targets. It was never meant to, being primarily a safety measure, but one could argue that the shortcoming was less important in previous times because the target array was rather different. Formerly, we thought of ground forces as being concentrated more narrowly at the front, with only a relatively small reserve held out of the fight. Away from the point of contact, there was a rapid diminution in targets that could have a near-term impact on the battle.

Our present view is of a battlefield of great depth, featuring the arrangement of enemy forces in a succession of echelons. For example, the standard depiction of Soviet-style echelonment shows the first-echelon division in the area from zero to thirty kilometers from the FLOT. (See Figure 1.) This places it inside the nominal FSCL. The first-echelon division includes two sets of targets: (1) first-echelon regiments, in the zone from zero to fifteen kilometers, deployed for combat, and either in contact or "close proximity." Obviously, this is the CAS target set; and (2) second-echelon regiments, in the zone from fifteen to thirty kilometers, in tactical march column, moving to contact, but not yet in "close proximity" as usually defined. This is the leading edge of a series of formations we lump together under the heading "second echelon," the elements of which extend rearward to considerable depth. We are likely to see at least the second-echelon regiments of the lead division inside the FSCL. Fire support coordination line placement beyond thirty kilometers (which we can expect) would also incorporate some elements of the secondechelon division.

Clearly, we must attack the second-echelon target set. We could even argue that, in some respects, it is an easier target than enemy forces in contact. Second-echelon vehicles will likely be lined up on roads instead of dispersed, under cover, mixed in with our own, etc., and at least some organic air defenses will be buttoned up for travel. It is of special importance that we attack second-echelon targets inside the FSCL,

since these targets constitute a more-or-less immediate problem for the ground commander. However, second-echelon elements found inside the FSCL do not fit in the CAS mission category. In fact, they occupy the hypothetical "no-mission zone" described earlier.

How Interdiction Has Changed

Just as the tactic of echelonment has changed our view of enemy force deployment on the battlefield, so too has there been an evolution in thinking about the interdiction mission. Conceptually, interdiction has always been a mix of attack on enemy forces and attack on transportation infrastructure supporting movement of these forces. But up to the mid-'70s, the main emphasis was on "isolating" the battle

field, reducing the flow of men and materials by attacking the line of communications (LOC) infrastructure. The point was often made that, by contrast with CAS, where effects are immediate, there is a time lag associated with interdiction effects. A good example of this view appears in the March 1973 version of Army Field Manual 100-26, The Air-Ground Operations System:

The effect of an air interdiction campaign seldom is immediately apparent. A coordinated and sustained effort based on sound intelligence and an analysis of the enemy logistic system is required to achieve results.

Naturally, we continue to think of interdiction as involving attacks on LOC infrastructure, but there has been a gradual shift in emphasis, with much more attention now given to

30-72 hours

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15-30

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5-15

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attacking enemy main force units as they move to contact. This changing emphasis can be seen in our doctrinal treatment of the interdiction mission. We are now giving much more attention to "battlefield air interdiction" (BAI).

Our concept of BAI-what it is, how it is controlled, etc.-is still evolving. As of the end of 1984, TAC and TRADOC had defined BAI as follows:

Air interdiction (AI) attacks against land force targets which have a near-term effect on the operations or scheme of maneuver of friendly forces, but are not in close proximity to friendly forces, are referred to as battlefield air interdiction (BAI). The primary difference between BAI and the remainder of the air interdiction effort is the nearterm effect and influence produced against the enemy in support of the land component commander's scheme of maneuver.10

To recapitulate, the second echelon-enemy forces stacked up behind elements in contactis the BAI target set. At least some of this target set will be inside the FSCL.11 Since these enemy forces can already affect friendly ground maneuver, it is not enough to delay or degrade them using the time-honored method of attacking LOC infrastructure. Immediate effects are required. We must attack BAI targets directly, with the purpose of destroying them.12

BAI versus CAS

How are we to attack the BAI target set? What control measures apply? One answer would be to consider BAI targeting a part of the CAS problem. Targets, munitions selection, and attack timing would be the responsibility of the ground commander. Detailed planning and execution control would be done by tactical air control parties (TACPs).

There are a number of good reasons-which can be dealt with here only in outline-why we should not attack the BAI target set within the framework of the CAS system:

• Combat featuring echeloned enemy forces is likely to be characterized by high-threat con

ditions. These circumstances may restrict employment of our primary CAS aircraft, keeping them near the FLOT and thus preventing their use against BAI targets. While important, this problem is not of overriding significance, since ! we have high-performance aircraft that can be tasked for the CAS mission.

• It may not be possible to provide terminal control for CAS missions back to the FSCL. This, too, is not an insurmountable problem, since we might be able to use "Fast FACs" or operate under "procedural" rather than direct | control.

Some in the Army may feel shortchanged because of a perception that we are spreading CAS over too large a target base. According to this view, the total CAS apportionment is for use in the narrower, "close proximity" band. Many would hold that CAS assets are not sufficient for this purpose and the resource would be fatally diluted by assignment to targets that ought to be attacked by aircraft from the AI apportionment category.

A more serious problem is that we may be required to "package" CAS. There is no nearterm prospect that TACPS serving with Army maneuver units, including the corps ASOC, will have the capability to put together "packages" with all the various kinds of support required-fighter cap, Wild Weasels, EF-111s, Compass Call, tankers, etc. Accordingly, if we insist that the BAI target set be attacked as if it were a CAS problem, then many of the planning responsibilities for CAS would have to migrate from the ASOC to the air commander's tactical air control center (TACC), the only place where such "packaging" can be done. This move would be a particularly unfortunate reversal of our conviction about decentralizing planning and execution of CAS.13

. Finally, there is no doubt that the requirement for "detailed integration" reduces our flexibility in the application of TACAIR. The CAS system has stood the test of time, it works well, and it is worthwhile to trade off flexibility when safety of friendly troops is at stake. But