Over-the-Horizon Amphibious Operations

by LtCol Jerome F. Bierly and Maj Thomas E. Seal

On 15 March 1991 LtGen Ernest T. Cook, Jr., commanding general, Marine Corps Combat Development Command (MCCDC), signed the Over–the–Horizon (OTH) Amphibious Operations Operational Concept. This concept will provide the basis for determining amphibious assault requirements for the next 20 years.

Development of an OTH assault capability is imperative for two reasons. First is the threat to traditional amphibious forces posed by naval mines and precision-guided munitions. The use of antiship missiles in the Falklands War, light antiaircraft missiles in Afghanistan, and our more recent experiences with naval mines and antiship missiles in the Persian Gulf serve notice that heretofore militarily insignificant states now have the potential to seriously challenge larger, modern forces. Second, the proliferation of weapons of mass destruction and improved delivery means pose a further problem to concentrated forces ashore or afloat. While these obstacles are not insurmountable, they compel a number of changes in doctrine, training, and equipment.

OTH is much more than a traditional amphibious landing from a greater range. Launched from beyond visual and radar range (usually in excess of 25 miles), the OTH concept is a logical step in the evolution of amphibious warfare. Dating from the development of the helicopter after World War II, the first official mention of an OTH requirement was in 1948. While we possess a limited capability today, full realization of the concept requires both new technology and a wider doctrinal view of amphibious operations.

OTH and Maneuver Warfare

We can no longer expect to fight an evenly matched or numerically inferior opponent. Therefore, we cannot afford to exhaust combat power in a war of attrition. FMFM 1, Warfighting, outlines our philosophy of maneuver warfare, a philosophy deeply ingrained in the essence of amphibious warfare. The OTH concept enhances the flexibility inherent in amphibious operations, broadening their scope as a seaward extension of maneuver warfare. Our ability to conduct such operations will improve as we institutionalize doctrine and training, modify force structure, and acquire advanced equipment.

Improvements in ship-to-shore mobility, command and control capabilities, and long-range fire support provide the means to apply maneuver warfare in an amphibious context. These improvements allow us to threaten a larger area and project forces inland far more rapidly than before, thus achieving objectives quickly and with fewer casualties. Essentially, these improvements equate to enhanced tactical mobility, operational speed, and operational flexibility-the keys to success in maneuver warfare.

Tactical mobility provides the freedom and ability to maneuver. When combined with firepower, tactical mobility becomes the principal physical ingredient of maneuver, enabling us to achieve a positional advantage over our enemy. Anything that enhances our ability to move or react quickly improves our ability to conduct maneuver warfare and OTH amphibious assaults. For this reason, the Marine Corps must continuously examine its operational requirements and the potential applications of new technology.

Enhanced tactical mobility offers many practical advantages. Capitalizing on the enemy’s inability to defend every potential landing site, the extended range and speed inherent in OTH enables the landing force to achieve surprise and concentrate strength against critical enemy weaknesses. By implication, this enhanced mobility complicates the enemy commander’s defensive problem. Barrier, obstacle, and countermobility plans become increasingly unmanageable. The enemy’s command and control problem also grows in direct proportion to the landing force’s mobility, diluting enemy cohesiveness and creating uncertainty in the mind of the defending commander.

Operational speed/tempo enables a commander to seize the initiative, shape the battle, and keep the enemy off balance. In maneuver warfare we strive to operate faster than the enemy can react. By decentralizing decisionmaking, gathering and processing intelligence rapidly, and reacting to battlefield chaos faster than our enemy, we place him in a situation where he cannot effectively function. This creates confusion and hesitation on his part and, in its ultimate form, panic, paralysis, and loss of the will to resist. Our operational tempo must exceed the enemy’s so that we may exploit opportunites and maintain the initiative, thus dictating the terms of the conflict.

Operational flexibility derives from the successful application of combined arms. A Marine air-ground task force (MAGTF) presents the enemy with a dilemma. If the enemy postures to counter one element of the combined arms force, he becomes vulnerable to the capabilities of another. For example, massing to counterattack leaves him vulnerable to supporting arms. Conversely, dispersing to avoid the ravages of supporting arms opens gaps vulnerable to exploitation by mobile forces.

There are two primary reasons to conduct OTH amphibious operations. The first is to achieve a tactical advantage over enemy forces on the ground. The second is to counter threats to the amphibious task force (ATF) by launching our assault from farther out at sea. Operational speed, tactical mobility, and the firepower of our combined arms enables the landing force to attack along multiple axes, by air and surface. In so doing, the landing force creates confusion, disrupts the enemy’s planning, compounds his targeting problem, and denies him the opportunity to attack concentrated and relatively immobile forces.

Our tactical mobility forces the enemy to counter the landing with a mobile defense. This defense relies on mobile reaction forces and indirect fire to provide a quick response to landing force incursions. This defense has several inherent vulnerabilities; these include a greater reliance on the initiative of subordinate commanders, dependence on effective intelligence to determine the time and place of landing, the need for more fire support to cover the expanded battlefield, and the command and control difficulties posed by a fluid, nonlinear battlefield. The OTH concept targets all of these vulnerabilities.

Executing OTH

Successful execution of future amphibious operations requires mastery of abbreviated, flexible planning techniques to cope with reduced warning and reaction times. To be successful, planners must anticipate likely missions, have good intelligence, know their responsibilities, and practice standardized plans and procedures until they become second nature. Employing the technique of “intelligence pull,” commanders must make such basic decisions as selection of landing zones and landing beaches virtually at the last minute. A firm understanding of the commander’s intent and flexibility at all levels are imperative.

Intelligence requirements for OTH will far exceed those of traditional amphibious operations. An OTH-capable amphibious force can threaten a thousand-mile coastline within a 24-hour period. The landing itself will cover a much greater area than in the past, both in terms of coastline available for surface landing and the depth to which airlifted forces will be inserted. Collecting, analyzing, and disseminating information will therefore be much more difficult in tomorrow’s wide-ranging operations. The landing force commander will require national intelligence collection products and an expanded analysis capability. Expertise in acquiring, processing, and evaluating national level intelligence data must therefore be resident in the landing force. Additionally, the ability to fuse intelligence from all sources, identify that which is needed by various echelons of command, and rapidly disseminate that information in a usable form, both afloat and ashore, is critical to success.

In OTH operations beaches and landing zones serve only as points of entry and control measures for landing forces. The point of OTH is to get mobile, combined arms teams ashore quickly, merge them into combat formations while on the move, and drive deep into the enemy’s rear. These multiple formations need not be mutually supporting in the traditional sense of supporting each other by fire. Their combined actions must, however, contribute to the confusion and dislocation of the enemy commander by making his preplanned defenses irrelevant. While pushing inland, the mobile forces will avoid the enemy’s fixed defenses, obstacles, and likely fire sacks in favor of drawing enemy counterattack forces into a meeting engagement. This tactic renders obsolete the traditional practice of seizing a beachhead to organize for land combat and to prepare for a massive logistic buildup. By implication, it also produces two tactical advantages. First, it avoids creating a lucrative target for the enemy. Second, it precludes a drawdown from the landing force to defend a beachhead with its attendant cost of slowing the pace of the operation.

New logistics equipment and procedures will be needed to support the landing force during OTH operations. The emphasis will be on unit distribution to support long-range, rapidly moving mobile forces. Coming from a sea-based rather than land-based logistics facilities, resupply of committed forces will be more difficult in OTH. Revised procedures for reporting, delivering, and tracking inventories and usage will be required. New items of equipment may also be needed to accomplish these tasks.

Representative Operation

In Marine expeditionary force (MEF) operations, aircraft will land self-contained, combined arms forces well inland, beyond prepared defenses. This could include regimental landing teams inserted some 40 kilometers beyond the beach into gaps in the enemy’s defenses. The mission of such vertical assault forces will be to threaten enemy command and control facilities, logistics sites, and lines of communication. Landing zones will be on the flanks of or behind enemy positions. Aircraft flight paths will be circuitous and at low level to avoid known enemy air defenses and observation, thus increasing the need for speed and range of aircraft.

The surface assault force, also a regimental landing team, will attack across multiple, widely dispersed points of entry. Landing as battalion landing teams, or even as reinforced companies, each specific landing team will be a task organized, self-contained, mobile combined arms force. The mission of each landing team will be to land across a narrow beach, quickly consolidate while on the move, and thrust deeply inland. If one landing team is unable to avoid or suppress opposition, the actions of the other teams should serve to make the defender’s position untenable. The preferred method of meeting the enemy will be to consolidate the advancing landing teams and engage his counterattack forces in a meeting engagement. This allows us to capitalize on our operational speed and tactical mobility.

The surface landing force can expect to encounter mines in shallow water, in the surf, and on the beach. A minefield is a “surface” that the landing force must avoid whenever possible and breach only if necessary. The key to mine avoidance is mine detection. To facilitate rapid planning, minefield locations must be identified and rapidly passed to higher headquarters. The tactical organization and formation of surface waves must minimize exposure to shallow water mines while en route and to land mines once ashore. Although the Navy retains the responsibility of clearing mines up to the high-water mark, the Marine Corps must aggressively pursue all ways to counter the mine threat Perhaps more than any other enemy tactic, effective minefield placement can hinder a surface assault and operations inland.

As with traditional amphibious landings, vertical and surface assaults can occur simultaneously or sequentially. They are designed to be complementary and either can represent the focus of effort. A mobile, sea-based exploitation force can be held aboard ship to influence the action ashore. Normally organized around a reinforced infantry regiment, this force can land by air, surface, or a combination of both.

Continued Development

Although already published, the OTH concept is far from complete. It is a dynamic document that will evolve through continued study and application. In the meantime, the Warfighting Center continues to develop supporting concepts of command and control, combat service support, aviation, and fire support. Through such vehicles as an OTH Working Group, studies, and lessons learned, the Warfighting Center gathers ideas, refines them, and incorporates them where warranted. Given the importance of the concept and its far-reaching effects, all Marines should contribute to this effort.

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