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Updating river-crossing doctrine: who and when?

When I reviewed the first draft of Field Manual (FM) 3-93, Decisive Force: The Army in Theater Operations, one line early in the manual caught my attention: "As a doctrine-based organization, the foundations of the Army's doctrine for full-spectrum operations are found in FM 3-0 (formerly 100-5), Operations."' This made me think of three things:

* FM 100-5 was the capstone document for doctrine throughout my career. Its importance to winning the Cold War and many other hot conflicts, especially Desert Storm, cannot be underestimated. This quote about "doctrine-based organizations" and FM 100-5 reminded me just how important doctrine is. We are truly a doctrine-based organization and are only as good as our written foundation.

* Headlines in the Army Times stated, "Rock Bottom- Training Centers Report They Can't Meet the Mission" (2) and "Training Command the Hardest Hit in Manning Plan." (3) Our doctrine is written at the training centers. If they area' t supported, our doctrinal base will not be updated. We will be stuck on a single step in the never-ending staircase of military evolution. My concerns were confirmed when I called the Engineer School and learned that its doctrine cell consisted of three people and was being reduced to two in the near future.

* I encountered a doctrine problem in the 2d Infantry Division concerning river-crossing operations. The essence of this problem was rafts versus bridges.

Rafts versus Bridges

During my last assignment as the engineer brigade commander for the 2d Infantry Division, I was very fortunate to have a bridge company as part of the brigade. My previous engineer assignments were with the 25th Infantry Division and the 101st Airborne Division. Ia these light organizations, river crossing wasn't on our mission-essential task list, so we simply didn't train on it. The last time I planned and participated in major river-crossing operations was as a company commander in the 1st Armored Division during Reforger 79. During my four-plus years with this division, we conducted numerous river crossings. The primary lesson we learned with mobile assault bridges (MABs) and the "new" ribbon bridge was that you bridge as soon as possible. We rafted only when we couldn't get a bridge in quickly enough to support the maneuver commander's plan. There was some risk, but it was offset by the much greater buildup of combat power afforded by bridges. During Reforger 79, we went straight to bridging. Our combat power built up and quickly overwhelmed the opposing force--1st Tank seized and maintained the initiative until the end of the exercise.

At the 2d Infantry Division, I ran into the doctrinal problem of rafts versus bridges. During a planning session, I commented that as a general rule I recommended rafting only when there were not enough assets to build a bridge. The response was, 'This isn't our doctrine; we raft to build initial combat power and then transition to bridges." We discussed that the decision to bridge immediately was a situational decision based on the calculus of combat-power buildup and the level of risk the commander was willing to accept. Even so, my audience still believed that rafting operations are a necessary part of doctrinal river-crossing operations. They provided direct quotes from FM 90-13, River-Crossing Operations, to support their argument.

In reviewing FM 90-13, I discovered that there were very few references to immediate bridge construction. They were limited to the following:

"Commanders may consider immediate construction of a bridge during this phase (Phase II - Assault Across the River) without ever conducting rafting operations. The advantage is that the combat power can be massed on the far shore at a much faster rate. The risk that the commander takes in making this decision is that a larger amount of bridging assets is exposed to enemy fire before the elimination of enemy indirect fires on the crossing area." (4)

"Since vehicles cross rivers much faster on bridges than on rafts, early bridge assembly is desirable but must be weighed against the risk that the enemy can still bring indirect fires down on an immobile bridge." (5)

References on the need for rafting were much more numerous and included the following:

"Bridges replace or supplement rafts once enemy-observed indirect fire is eliminated." (6)

"The urgent need to get tanks across the river means the rafting stage often begins before terrain on the far shore is secure to the planned (release line) RL." (7)

"Heavy rafts are prepared to transport tanks and infantry fighting vehicles to the far shore for reinforcing the dismounted infantry." (8)

"Enemy indirect fire into the crossing area will probably continue; however, each crossing site within the crossing area must be isolated from direct fire to enable the construction and operation of rafts. These rafts will then be used to transport armored vehicles for rapid reinforcement of the dismounted infantry task force." (9)

"Rafts are usually the initial means for crossing non-swimming vehicles--particularly tanks--on wide, unfordable rivers. It may be possible to bridge immediately after the assault across the river; however, rafting is normally first because rafts--

* Are less vulnerable to enemy air and indirect fire due to their size and maneuverability.

* Are quicker to assemble.

* Offer more flexibility in operation, particularly in site selection and subsequent movement between sites.

* Can use existing road networks and banks where access and exit routes are not aligned opposite of each other." (10)

Consider the following--

"A river crossing is a race between the crossing force and the enemy to mass combat power on the far shore. The longer the force takes to cross, the less likely it will succeed as the enemy will defeat, in detail, the elements split by the river. Speed is so important to crossing success that extraordinary measures are justified to maintain it. The commander must allow no interference with the flow of vehicles and units once the crossing has started." (11)

The calculus of force buildup is greatly enhanced by immediate construction of bridges if the situation allows. To close a 150-meter gap on the Imjin River, where we routinely trained, with one construction site took about 90 minutes. At this point, we could begin crossing vehicles at the rate of 200 an hour. If we initially built the two rafts that can be accommodated with a single centerline on a 150-meter gap, we could cross 14 M1 tanks in 95 minutes.

Five minutes after the bridge went into operation, it began to exceed the crossing capability of the rafts. It could cross 33 vehicles every 10 minutes versus the two vehicles crossed by the rafts. This is a significant payoff that must be considered and not ignored due to the wording and structure of our doctrine. (See the table on page 22 for the vehicle-crossing timelines.)

Why doesn't our doctrine explain how to compare bridges to rafts and definitely say that going immediately to bridges is a serious option? My initial thoughts were that we were still using doctrine based on old time-intensive bridge systems. As a platoon leader, I had experience in building Class 60 and M4T6 rafts. For trained troops, building a Class 60 raft capable of carrying an M60 tank took 50 minutes if the pontoons were preinflated and combat-loaded and 90 minutes otherwise. For the equivalent M4T6 raft, it took 100 minutes. (12) For both types of bridging, it took 3 to 5 hours to build the 150-meter bridge required for the Imjin River example. (13) I believed that since it took so long for bridge construction, these bridge systems forced us to initially build rafts. This suspicion led me to the Military History Institute, where I reviewed all available river-crossing publications beginning with one dated 31 January 1941 to the present one dated 26 January 1998.

As I reviewed the various manuals, I was surprised--especially by the post-World War II publications. The manuals of the 1940s depended heavily on various rafts with the standard rafting operations followed by bridging operations. The first field manual I found that was totally dedicated to river crossing was FM 31-60, River-Crossing Operations, dated August 1952. Based on the date, I assumed that it incorporated lessons from World War II and the initial lessons from the Korean War. Following are some of the more interesting quotes:

"While it is desirable to delay [bridge] construction until the construction site is relatively safe from observed artillery fire, the responsible commander must evaluate the effect of delaying erection on his mission against losses of trained personnel and equipment. " (14)

"The following factors must be considered before heavy-bridge construction is ordered:

(1) The mission.

(2) The tactical and logistical support required by forces on the far side of the river.

(3) The amount of available and reserve bridging.

(4) The accuracy and intensity of enemy air attacks and artillery fire on the bridge site.

(5) The probable danger of loss of the bridgehead if sufficient armor cannot be crossed until the bridge is in.

(6) When additional bridging material is unavailable, the effect on the operation if the bridge were destroyed by the enemy.

(7) Availability and use of smoke-generating equipment." (15)

"Rafts are an excellent means of putting the high-priority essential vehicles into the bridgehead during the interval between the assault crossing and the completion of bridges. Employing men and equipment on raft construction and use, however, may retard the building of bridges. It takes almost as long to build a raft and to put it into operation as it does to build a bridge to span a stream which is 150 feet or less in width." (16)

"Bridges are constructed after the second objective (a position that eliminates the enemy s observed fires) is taken or earlier if enemy artillery fire proves to be ineffective, has been rendered so, or has been neutralized." (17)

Manuals up into the 1970s continued to reflect this more aggressive use of bridges, to include the 1972 version of FM 31-60 that I used with the 1st Armored Division. It included the following information:

"Failure to construct bridges early in the operation may result in delaying the advance beyond the river. This may allow the enemy time to reinforce with sufficient strength to delay or prevent securing the bridgehead." (8)

"The initial advantage of speed in commencing operation of rafts may be more than offset by the greater efficiency of bridges that can be placed in operation in a short time. Construction of bridges begins as early as possible." (19)

"If sufficient MAB equipment is available, consideration must be given to employing it as a bridge early in the operation. Assembly times are shorter when compared to other types of float bridges. In addition, if enemy fires should increase to a level endangering the bridge, the MAB units can rapidly disengage from one another and be reconfigured as rafts until the fires subside. (20)

I find it interesting that the older manuals address constructing bridges as soon as possible and go into more detail than our current manual does on considerations for omitting rafting. Going immediately to bridging should not be ruled out just because it is only addressed by four sentences in our doctrine. We need to emphasize the importance of rapidly building combat power and consider going straight to bridges. Immediate bridging operations should be a serious course of action for all river-crossing operations. The experiences gained during World War II, the Korean War, and the Cold War should not be forgotten by current doctrine. They must be overtly reflected in our current doctrine for planning considerations. We cannot raise a new generation of sapper warriors who don't seriously consider all options. This is especially important since American large-scale river-crossing experience is rapidly shrinking. With only a handful of active duty bridge units, we have largely lost our "hands-on experience." T his makes doctrine even more important. Future generations of engineers will depend on it.

Summary

In the narrow scheme of things concerning river-crossing doctrine, we need to capture our experiences and include the considerations for going straight to bridging. We must make it a possible course of action and check the calculus to see if the benefits are worth the risk for the maneuver commander. Don't just ignore this option due to a doctrinal deficiency. As a doctrine-based organization, we must update our doctrine as our systems change, to provide more flexibility. Decision makers need to be empowered and not shackled with a doctrine that no longer fits the bill. Let's start the dialogue to help the Engineer School update our doctrine.

Who... and when? Us... and NOW!
Number of Vehicles Crossed

Minutes 25 35 45 55 65 75 85 95 105 115 125
Two Rafts 1 2 4 6 8 10 12 14 16 18 20
Bridge 0 0 0 0 0 0 0 16 49 82 115


Endnotes

(1.) FM 3-93 (100-7), Decisive Force: The Army in Theater Operations, First Draft, July 2000, PP. 1-14.

(2.) Sean D. Naylor, "Rock Bottom," Army Times, 11 September 2000, p. 8.

(3.) Sean D. Naylor, "Training Command the Hardest Hit in Manning Plan", Army Times, 4 September 2000, p. 10.

(4.) FM 90-13, River-Crossing Operations, 26 January 1998, p. 5-8.

(5.) Ibid, pp. 7-14.

(6.) Ibid, pp. 7-13.

(7.) Ibid, pp. 3-11.

(8.) Ibid, pp. 5-6.

(9.) Ibid, pp. 5-8.

(10.) Ibid, pp. 7-9.

(11.) Ibid, pp. 1-6.

(12.) FM 31-60, River-Crossing Operations, 27 March 1972, p. 60.

(13.) Ibid, p. 67.

(14.) FM 31-60, River-Crossing Operations, August 1952, para. 45.

(15.) Ibid, para 45.

(16.) Ibid, para. 62.

(17.) Ibid, para. 63.

(18.) FM 31-60, River-Crossing Operations, 27 March 1972, pp. 3-19.

(19.) Ibid, pp. 3-28.

(20.) Ibid, pp. 3-28.

Colonel Littlefield (now retired) was assigned to the U.S. Army War College's Department of Military Strategy, Planning, and Operations when he wrote this article. He previously commanded the 2d Infantry Division's Engineer Brigade. A graduate of the United States Military Academy, COL Littlefield holds a master's degree in operations research/systems analysis from the Naval Postgraduate School. He was a joint specialty officer and is a registered professional engineer in the state of Virginia.
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Author:Colonel Littlefield, Thomas K., Jr.
Publication:Engineer: The Professional Bulletin for Army Engineers
Geographic Code:1USA
Date:Jul 1, 2002
Words:2345
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