In an October 2007 press release, the Commandant of the Marine Corps, General James T. Conway, stated that he was concerned that in the wake of the war in Iraq his service was becoming a "second land army" and was losing its expeditionary character and its "ability to launch amphibious support."1 Being a complicated, inherently joint proposition, the many aspects of an amphibious operation must be revisited and examined if proficiency is to be regained. This call for a renewed Marine Corps emphasis on amphibious maneuvers comes nearly 60 years after the last major amphibious action, General Douglas MacArthur's bold Korean War assault at Inchon. The Inchon operation provides an illustrative case study to analyze how the challenges of an unknown amphibious battlespace were overcome through hydrographic support and how such information fed to the operational commander was critical to mission success. The Inchon operation demonstrates a central thesis: Hydrographic support is a vital skill that must be maintained and exercised as a core competency for amphibious operations.
Amphibious Hydrography Reinvented
During World War II, Rear Admiral Richmond Kelly Turner, one of Admiral Chester Nimitz's amphibious commanders, designated a full staff position to his hydrographer, Commander Ira Sanders.2 Although Sanders contributed greatly to Turner's operational successes, none of his practices were codified at the time in a combat service publication, as post-war leaders saw little future for amphibious operations.3 However, just five years after World War II, General MacArthur found himself planning exactly that kind of operation.
Nineteenth-century warfare theorist Antoine Henri Jomini stated that the two keys to a successful amphibious attack are deception and knowledge of the nearshore environment. For his momentum-changing assault, MacArthur chose to make use of both in putting troops ashore at the "unlikeliest harbor on the peninsula: Inchon."4 Its tidal range was the second highest in the world at 33 feet.
Strong currents of up to eight knots flowed through Inchon Harbor's approach, Flying Fish Channel, while mudflats and banks extended thousands of yards from the seawall.5 Captain Norman Sears, one of MacArthur's planners, stated that "Flying Fish was well named. A fish had to fly to check his navigation past the mud banks."6 Furthermore, the very gradual gradient of the seabed approaching Inchon required a high tide of 23-29 feet, occurring only a few days per month, to support landing craft.7 "Not impossible" was the most optimistic statement that staff planners could muster.8 MacArthur however, recalling how the Navy had overcome challenging hydrography across the Pacific during World War II, was confident. "The Navy has never let me down in the past, and it will not let me down this time."9
The Navy, lacking a structured systematic approach to describing the physical amphibious battlespace, struggled to meet MacArthur's expectations. The first step to reinventing hydrographic support was to find data to address the numerous concerns pointed out by one of the planners: "We drew up a list of every natural and geographic handicap and Inchon had 'em all."10 MacArthur was fortunate to have a staff member, Air Force Captain Robert Miller, who had studied at Scripps Institute of Oceanography and could interpret and brief hydrographic data. Miller served as a clearinghouse for geographic data, publishing reports on currents, sea conditions, tides, water temperature, transparency, bottom sediments, and underwater contours.11 The support of an undesignated staff hydrographer was invaluable in allowing planners to construct a base plan for the operation.
Geographic data, however, were sparse for the region, so a haphazard plan was conceived to place Navy Lieutenant Eugene Clark on a small island near Inchon two weeks before the invasion. Clark's amphibious background made him ideally suited for the mission.12 His first job was to check the current chart, which was based on sounding data from a 1916 Japanese survey. Considering that the Han River in the delta north of Inchon had deposited silt for more than 34 years since the survey, the channel and approach required careful verification, with new obstacles charted and identified.13 Clark used a South Korean patrol craft to conduct a clearance survey by transiting the channel and verifying depths.
With the nautical chart verified, Clark began his amphibious beach surveys. Two vital pieces of information were required: tidal verification and beach composition. Clark commandeered sampans and personally conducted night beach surveys, radioing his information back to Tokyo for planners. He measured the extent of the mudflats and shoals and reported underwater obstructions. He also provided a detailed description of the beach slope and composition, enabling landing craft to be properly trimmed and not broach too far out to sea.14
Even more important to operational planners, Clark conducted tide observations and reported that Japanese tide tables were more accurate than American versions, enabling the 1st Marine Division commander to make informed critical decisions and pinpoint invasion timing at the two necessary high tides on D-Day.15 Referencing Clark's tidal data and beach survey, Marine commanders also were able to successfully beach a landing craft loaded with ammunition and supplies, providing vital logistics and sustainment for the beachhead.16
Yardstick of Success
Although woefully unprepared to support an amphibious operation, the success of the joint force's ad-hoc approach to such an extreme physical challenge was ultimately measured by the success of the landing. Marine Corps Brigadier General Edwin Simmons accurately stated that the "anticipated hydrographic conditions were much more frightening that the quality of expected enemy resistance."17 His statement highlights the importance of the challenges that the geophysical support team mastered. The specter of landing craft grounded and smashed in the surf, miles offshore or hopelessly stuck in mud banks, was averted, and the amphibious attack was a stunning success.
The hydrographic support to operational planners was absolutely vital to overcoming the many natural obstacles that misled the North Koreans into believing an attack impossible. Indeed, one of the main reasons MacArthur's Inchon plan is viewed as a stroke of genius is that he trusted his operational forces to overcome Inchon's geographic challenges. In his book about the influence of physical nature on battle, author Harold Winters noted, "MacArthur used the forbidding hydrography at Inchon to great advantage. The tides, mudflats, and limited access channel to the port all but excluded Inchon as an invasion site," allowing him to completely surprise enemy defenders.18
The success of Lieutenant Clark's and Captain Miller's work solved many of the operational problems facing the planners of the Inchon operation. On examining the scope of the information, the quality and relevance of Clark's beach and tidal reconnaissance information, and the thoroughness of Miller's geophysical data consolidation, planners realized that they were handed an operational intelligence coup that thoroughly prepared this particularly challenging battlespace for the amphibious force. Clark's memoir of the operation, appropriately titled The Secrets of Inchon, reflected the reality that hydrographic support truly was one of the keys to the landing's success.
The vital role hydrographic reconnaissance played at Inchon gave new hope to those who wanted to reinvigorate the amphibious staff hydrographer concept that Rear Admiral Turner had used with success in World War II. Five years after Inchon, Commander Sanders produced a document for the Naval Hydrographic Office delineating the roles and responsibilities of the "Force Hydrographer" for "Amphibious Wartime Conditions."19 In his document, Sanders proposed a role for a staff officer that would serve as the clearing house for all geodetic data to be used as part of the intelligence assessment and operational planning effort, much like Captain Miller had done on MacArthur's staff at Inchon.20 However, any momentum gained by the success at Inchon was dulled by the lack of amphibious operations in the following decades. The staff hydrographer role never materialized with any staying power, and the skills and knowledge of hydrographic amphibious support gradually eroded with disuse.
Today's Amphibious Hydrography
The Inchon operation has been described as a classic example of military strategy. At the center of this stunning success are three main conclusions concerning the use of hydrographic support for the amphibious commander: It is an indispensable component of amphibious operational planning; it is of critical importance to the operational commander's decision making process; and it is a core competency of amphibious operations that needs to be sustained to support the viability of amphibious operations.
In the wake of the 2003 Iraq War, the Marine Corps is making a concerted effort to regain its traditional mastery of the amphibious environment. Therefore, the present offers an excellent opportunity to re-engage hydrography with the amphibious commander. As the Navy and Marine Corps rebuild the foundations of amphibious operations, it is critical to build a framework that takes advantage of all available tools and capacities to establish a capability that is successful across a wide range of missions.
Inchon demonstrates the importance of hydrographic support to the planning process as those efforts were the centerpiece of the informational preparation of the battlespace. During Lieutenant Clark's mission, more attention and assets were actually assigned to obtaining nearshore environmental data than spotting troops and gun emplacements. Throughout the planning process, hydrography was clearly identified as a leading information requirement and therefore was fulfilled with high priority.
Hydrography remains an important requirement for contemporary amphibious planning. Its need is stated in the introductory sentence of the U.S. Navy's Joint Surf Manual. With modern amphibious operations emphasizing the use of amphibious assault vehicles (AAVs), the Marine Corps Warfighting Publication (MCWP) on the vehicles states, "hydrography . . . will be required to effectively employ AAVs to negotiate the seaward approaches and to move from the surf zone to inland objectives," and identifies hydrographic data as "must haves" for operational success.21 The Joint Publication for Amphibious Operations agrees on its importance to planning, and the Joint Warfighting publication Ship-to-Shore Movement dictates that the key, specific planning considerations regarding maneuver from sea to shore are mainly affected by the considerations of "hydrographic features of the beach and approaches."22
Currently, a staff intelligence officer would consider the physical environment for an amphibious plan as part of the Joint Intelligence Preparation of the Operational Environment process. However, considering the importance emphasized in current warfighting publications, future doctrine needs to codify the involvement of an officer with a military hydrographer additional qualification designator in the fundamental planning steps and decision making bodies of an amphibious operation to provide an accurate and timely assessment of nearshore geodetic conditions.
Hydrography was also clearly critical at Inchon to the operational commander's timely decision-making process. Tidal observations directly influenced the decision to divide the assault into two phases using the two high tides at morning and dusk while also impacting logistical sustainment decisions.23 In the incredibly challenging environment, operational decisions keyed on tides and beach geography to an indispensable extent, making hydrography a most vital operational decision making tool.
Most Crucial Information
As at Inchon, current doctrine supports hydrography as a commander's critical information requirement-one in the decision making process that affects successful mission accomplishment-for an amphibious operation. The warfighting publication for AAVs states, "the success or failure of an amphibious landing . . . largely depends on the completeness and accuracy of (hydrographic) intelligence data and upon . . . interpretation of that data."24 The joint Ship-to-Shore Movement publication declares that "hydrographic features of offshore areas" are "principal considerations" that shape the operational decisions of ship-to-shore movement.25 At Inchon, if Lieutenant Clark had radioed back the discovery of unknown impediments that could potentially preclude the amphibious operation, the information would have had flash priority to be passed to General MacArthur upon receipt to restructure or cancel the assault. Clark's reconnaissance was a clear decision point during the Inchon operation as it confirmed to the general that the objective could be successfully attacked from the sea and also supplied key information for operational decisions as the attack progressed.
A good operational commander will push the envelope of his staff's ability to solve complex problems whose solutions may require a variety of information to satisfy their requirements. On hearing of MacArthur's decision to land at Inchon, the operational staff groped clumsily for an ability to obtain key geographic intelligence. The skill set of hydrographic preparation of the amphibious battlespace had been neglected for five years after World War II and struggled to reinvent itself at Inchon until a Navy lieutenant and an Air Force captain stepped forward. Lacking the data provided by these two officers, successful mission accomplishment would have been much more questionable.
There must be an understanding at the joint level for amphibious operations to the priority and maintenance of hydrographic support. The critical strength of an amphibious force is its ability to arrive from the sea and project power ashore. Knowledge of the physical environment is a critical data requirement, supporting this strength and enabling it to leverage its full advantage. An active effort must be realized to ensure hydrography remains functional in the amphibious domain. As amphibious operations are reengaged within the Marine Corps, amphibious planners and military hydrographers need to train toward the support requirement, stepping into the breach to become part of a permanent developing doctrine. The risky prospect of reinventing a hydrographic capability when assigned an amphibious operation is not an option in the short-fused, immediate-response environment of today's military. Innovations and new technologies, such as unmanned underwater vehicle sensors, need to be vetted and lessons learned applied to further develop hydrographic capabilities and maximize their contributions across the planning and execution phases of an operation. Hydrographic expertise must be ready on the shelf to enable amphibious operations as an effective option.
Put Hydrography in the Loop
In light of current warfighting publications and past experience, it is clearly essential that an operational staff be able to accurately interpret hydrographic data. The function of a mandated hydrography staff officer would be very similar to the role envisioned by Commander Sanders after the Korean War. He would serve as the clearinghouse for all hydrographic data, whether derived from open source, satellite, air, unmanned vehicles, or beach surveys done by SEALs or Marine reconnaissance. The staff officer would assess the quality of the data and work closely with the operational planning cell to make certain that plans are realistic and feasible. During the operation, he would ensure that data is efficiently transferred and properly understood for critical decision-making. When planning or decision making time is limited and insights and assessments are required in real time, a staff presence is vital toward addressing information at the commander's critical information requirement level.
Future amphibious operational planners and executers need to ensure that the key components and personnel are ready and in place to provide a planning and decision making foundation that leads to successful mission accomplishment.
1. Armed Forces Press Release, "Marine Corps Losing Expeditionary Flavor." 17 October 2007.
2. Charles C. Bates, HYDRO to NAVOCEANO (Rockton, IL: Corn Field Press, 2005), p. 82.
3. Ibid.
4. Harold A. Winters and William J. Reynolds, Battling the Elements: Weather and Terrain in the Conduct of War (Baltimore, MD: Johns Hopkins Press, 1998), p. 210; and William Manchester, American Caesar (Boston, MA: Little, Brown & Co., 1978), p. 573.
5. Winters and Reynolds, Battling the Elements, p. 210.
6. Robert D. Heinl Jr., Victory at High Tide (New York, NY: J. B. Lippencott, 1968), p. 27.
7. Ibid., p. 25.
8. Ibid., p. 40.
9. Manchester, American Caesar, p. 575.
10. Ibid., p. 574.
11. Bates, HYDRO to NAVO, p. 116.
12. Commander Eugene Franklin Clark, The Secrets of Inchon: The Untold Story of the Most Daring Covert Mission of the Korean War (New York, NY: G. P. Putnam's Sons, 2002), pp. 4-6.
13. Ibid, p. 49.
14. Clark, Secrets of Inchon, p. 250.
15. Ibid., pp. 262, 322.
16. Ibid, p. 323.
17. Brigadier General Edwin H. Simmons, USMC, Over the Seawall: US Marines at Inchon (New York, NY: Diane Publishing Co., 2000), p. 18.
18. Winters and Reynolds, Battling the Elements, p. 214.
19. Bates, HYDRO to NAVO, p. 286.
20. Ibid.
21. Marine Corps Warfighting Publication (MCWP) 3-13, Employment of Amphibious Assault Vehicles (Headquarters US Marine Corps, February 2005), p. 3-2.
22. U.S. Navy Warfighting Publication (NWP) 3-02.1/U.S. Marine Corps Warfighting Publication (MCWP) 3-31.5, Ship to Shore Movement (Department of the Navy, Headquarters U.S. Marine Corps, August 1993), p. 4-1.
23. Heinl, Victory at High Tide, p. 46.
24. MCWP 3-13, Employment of Amphibious Assault Vehicles, p. 3-2.
25. NWP 3-02/MCWP 3-31.5, Ship to Shore Movement, p. 1-3.