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This lesson outlines the fundamentals of river-crossing operations. It describes the three types of river crossings. To emphasize these fundamentals, the lesson includes a historical case study of an unsuccessful crossing operation.


ACTION: You will identify the three types of river-crossings and identify the river-crossing fundamentals.
CONDITION: You are given the material contained in this lesson.
STANDARD: You will correctly answer all practice-exercise questions at the end of this lesson.
REFERENCES: The material contained in this lesson was derived from FM 90-13/MCWP 3-17.1, JAN 98.


The purpose of any river crossing is to project combat power across a water obstacle. A river-crossing operation, by its nature, is a unique operation. Before you can understand the planning, C2, and execution of a river-crossing operation, you must understand the basic concepts. Chapter 1 of FM 90-13 provides a detailed discussion of these concepts.

1-1. Historical Case Study-The Rapido River Crossing. Throughout history, armies crossed rivers to engage or flee from enemy forces. The ancient Persian Army built bridges during their invasion of Greece in the fifth century BC. In the fourth century BC ancient Macedonia first used professional engineers to facilitate movement across rivers. Various ancient Roman armies frequently conducted river crossings to engage other armies. Dying out after the fall of Rome and Constantinople, river crossings again became common events when armies became mobile during the eighteenth century. Armies frequently performed river crossings during the Napoleonic Wars and the two World Wars. More recently, the Israeli Army crossed the Suez Canal to encircle the Egyptians after the Egyptians first crossed the canal during the 1973 Yom Kippur War.

a.   Although technology has improved crossing means, the basic fundamentals of attacking an enemy across a river have not changed since ancient times. A commander who violates these fundamentals becomes frustrated and fails to cross his force. Such was the case of the United States (US) 36th Infantry Division at the Rapido River in Italy during World War II.

b.   After the capture of Naples in October 1943, the Allied 5th Army Group, consisting of the US 5th Army and British 7th Army, focused on capturing Rome. General Earl Alexander of Britain commanded the 5th Army Group. The Allied High Command wanted General Alexander to gain a political victory in Italy. The fall of Rome would symbolize the crushing of the Berlin-Rome political axis. The Allied High Command also had a military reason to capture Rome. This would force the German Army to move units from Russia. It would also create a diversion from the Allied invasion of France. General Alexander ordered Lieutenant General (LTG) Mark Clark and the US 5th Army to capture Rome. For this battle, the US 5th Army consisted of the US II Corps (34th and 36th Infantry Divisions), the US VI Corps, the British X Corps (5th, 46th, and 56th Infantry Divisions), and the French Expeditionary Corps.

c.   The German commander in Italy, Field Marshal Albert Kesselring, had successfully used delaying tactics since the start of the Allied invasion of Italy. He nearly destroyed the Allied beachhead at Salerno because he delayed the relieving force long enough to mount extensive counterattacks against the Salerno beachhead. He established three defensive systems south of Rome-the Barbara Line, the Bernhard Line, and the Gustav Line-each being progressively stronger. The lines extended from the Tyrrhenian Sea across the Italian peninsula to the Adriatic Sea. To defend these lines, he commanded the German 10th and 14th Armies. His objective was to hold Allied forces south of Rome for the winter.

d.   Field Marshal Kesselring made General Baron Heinrich Von Vietinghoff, commander of the German 10th Army, responsible for defending the Italian peninsula south of Rome. The Gustav Line paralleled the Rapido and Garigliano Rivers in General Von Vietinghoff's sector (Figures 1-1 and 1-2). His engineers used the existing terrain for their defenses. They placed double-apron wire fences, booby traps, and trip-wired mines along all approaches to the rivers. The engineers also built slit trenches, dugouts, and concrete and steel bunkers along the line. His troops emplaced machine-gun and mortar positions in solid rock. They were ready to counter an Allied attack.

Figure 1-1.  Italy in early 1944

Figure 1-1.   Italy in early 1944

Figure 1-2.  The 5<SUP>th</SUP> Army's area of operations

Figure 1-2. The 5th Army's area of operations

e.   LTG Clark planned to attack the Gustav Line with two corps abreast. On the left, near the coast, the British X Corps was to cross the Garigliano River on 17 January. On the right, the US II Corps (specifically the 36th Division) was to cross the Rapido River on 20 January. Their immediate objectives were to gain entrance to the Liri Valley-the "gateway to Rome"-and to capture Mount Cassino.

f.   These were important objectives; however, LTG Clark's main objective was the US VI Corps landing at Anzio on 22 January. Anzio is 30 miles south of Rome and 50 miles north of the Rapido River. After landing, the US VI Corps's objective was Rome. The British X Corps and US II Corps attacks were part of a large deception plan. The two corps would occupy the German 10th Army and draw their reserves away from Rome. This diversion would prevent the annihilation of the US VI Corps during its initial landing and annihilate the German 10th Army.

g.   A successful British X Corps attack was essential to a successful US II Corps crossing of the Rapido River three days later. LTG L. K. McCreary, commander of the X Corps, planned to attack with two divisions abreast across the Garigliano River on 17 January. The 5th Division would occupy the Minturno Ridge on the left while the 56th Division occupied Castelforte in the center. Most critical to the US II Corps's attack was the 46th Division reaching the southern edge of the Liri Valley on the right. This would support the US II Corps's left flank during its Rapido River crossing.

h.   Opposing the British X Corps and the US II Corps was the German XIV Panzer Corps, commanded by LTG Fridolin Von Senger. The German 94th Infantry Division faced the British X Corps. The defense of this area concerned LTG Von Senger. The 94th Division was inexperienced and not well-trained. He resorted to using 24,000 mines to reinforce the division's defenses.

i.   The British attacked on 17 January. They took the 94th Division by surprise. By the morning of 18 January, the British X Corps had ten battalions with heavy weapons across the Garigliano River. The 5th Division occupied Minturno Ridge while the 56th Division surrounded Castelforte by 19 January. They opened one 30-ton M2 bailey bridge across the Garigliano River on 20 January.

j.   Realizing the potential Allied breakthrough, LTG Von Senger sent a request for the I Parachute Corps from the reserves held at Rome. Field Marshal Kesselring approved this request after receiving intelligence reports that enemy landings in Italy would not take place soon. The I Parachute Corps stopped the British advance.

k.   Not yet discovering the I Parachute Corps movement, LTG Clark insisted on sending the main thrust of his forces across the Rapido River on 20 January. The US VI Corps would land at Anzio on 22 January.

l.   While the British expanded their bridgehead, the US II Corps, commanded by Major General (MG) Geoffery Keys, prepared for its attack. The 36th Division, Texas National Guard, planned to cross the Rapido River at Saint Angelo. The division planned to force a crossing against prepared German positions and establish a bridgehead 241 miles deep. Meanwhile, the 34th Division was to tie down the German defenders in the Mount Cassino area. No reserves were available to exploit the initial attack.

m.   The 36th Division would not achieve surprise. The finest combat troops in LTG Von Senger's command (the 15th Panzer Grenadier Division) waited across the Rapido River. The division was well-trained and -equipped. Its soldiers were well-led, motivated, and combat experienced. The division was awaiting an attack. It built excellent observation posts in the Mount Cassino monastery and surrounding hills and built bunkers reinforced by obstacles along the entire front. LTG Von Senger saw no need to reinforce the 15th Panzer Grenadier Division. His main concern was the British X Corps breaking through the 94th Infantry Division to his left.

n.   MG Fred L. Walker commanded the 36th Division. Aware of the enemy's strength, he reluctantly planned his attack. His division engineer, Lieutenant Colonel (LTC) Oran Stoval, performed an extensive reconnaissance of the Rapido River crossing area. He found "an appalling lack of basic engineer supplies." Corps assets soon remedied this. The river was 25 to 30 feet wide and ran between near-vertical banks 3 to 6 feet high. Water flowed swiftly and the depth varied from 6 to 12 feet. Although small and unimpressive looking, weeds and brush covered its banks on flat, marshy ground. This made for good concealment of German mines.

o.   MG Walker planned to attack south of Saint Angelo with the 143rd Infantry Regiment and north of the town with the 142nd Infantry Regiment. He substituted the 141st Infantry Regiment for the 142nd Infantry Regiment after the rehearsals. He ordered a night attack because of the fixed German defenses. The German positions included excellent observation, fields of fire, and uncovered approaches to the river. MG Walker knew this violated an important fundamental-"night operations must be simple." MG Walker's outlook before the battle was pessimistic. His initial suggestion to LTG Clark was to attack on the other side of Mount Cassino. (Perhaps foremost in his mind was a day in World War I, when his inexperienced battalion slaughtered 10,000 German soldiers as they attempted to cross the Marne River.)

p.   In the meantime, LTG Clark's plan changed. The 46th Division was to begin its assault across the upper Garigliano River on 17 January. They hesitated to attack until 19 January. When they did attack, they did not cross the river. The 46th Division was to help the 36th Division by securing the 36th Division's left flank. Now the original plan was impossible to execute. As a result, MG Keys requested a delay in his crossing date. LTG Clark denied his request.

q.   Despite this setback, the 36th Division prepared for the attack. The 142nd and 143rd Infantry Regiments each conducted a rehearsal to practice handling river-crossing equipment. The 141st Infantry Regiment, which later substituted for the 142nd Infantry, received no such training. Close teamwork between engineers and infantrymen was lacking in this rehearsal. In addition, half the troops were inexperienced replacements in the regiments. The rehearsals did not reach their full potential in preparing for the crossing.

r.   Elements from three different engineer units assembled to support the 36th Division's river crossing. Two companies of the 16th Armored Engineer Battalion reinforced the division's organic 111th Combat Engineer Battalion for the assault. Together they had four critical tasks to perform—

    • Clear mines from the crossing sites by 20 January.
    • Construct and maintain bridge approaches and exits before, during, and after the assault.
    • Clear mines and roads in the bridgehead.
    • Build bailey bridges when the enemy fire ceased.

s.   The 19th Combat Engineer Regiment attached a battalion to both of the assaulting infantry regiments for the actual crossing. Each engineer battalion provided 30 pneumatic reconnaissance boats, 20 assault boats, and 4 footbridges.

t.   The 19th Combat Engineer Regiment could not move its equipment to the river. There were no roads to the crossing sites. German engineers had diverted the Rapido waters onto the flats, making them impassable to wheeled and tracked vehicles. The engineers dumped their equipment several miles from the crossing sites. Assault troops later had to carry the engineer equipment to the site, causing fatigue even before the operation began.

u.   As darkness fell the evening of 20 January, a heavy fog settled into the 36th Division's area. After preparatory bombardments from the division artillery, the corps artillery, and the air forces, the 1st Battalion, 141st Infantry began its assault. Deadly, accurate German artillery fire damaged and destroyed some boats where the 19th Combat Engineer Regiment had dumped them. The German artillery scattered infantrymen (who were carrying the assault boats) in minefields to seek cover. Confusion abounded as engineer guides became lost in the fog. They led troops into previously cleared minefields that were remined by aggressive German patrols. Many assault troops strayed, took cover from shells, or refused to cross. German artillery fire knocked out equipment as it entered the water. Still, the 1st Battalion, 141st Infantry managed to erect a single footbridge by 0400 hours on 21 January. With this footbridge and the remaining boats, most of the battalion crossed the river and dug in.

v.   On the right, the entire 1st Battalion, 143rd Infantry reached the exit shore by 1000 hours on 21 January. As daylight came, German artillery became more effective. A portion of the troops across the Rapido withdrew to the near bank resulting in more engineer equipment being damaged, destroyed, or lost in the swift-flowing river. The remainder of the troops became prisoners.

w.   Later in the morning, LTG Clark's intelligence officer informed him that the Germans were rushing their reserves to the area. LTG Clark probably did not know the enemy reserves were to block the British X Corps's bridgehead across the Garigliano River. LTG Clark directed MG Keys to "bend every effort to get tanks and tank destroyers across promptly." MG Keys ordered MG Walker to cross the Rapido River again early that afternoon. The 141st and 143rd Infantry Regiments were to renew their attacks in the same locations. The regiments postponed their attacks until 1600 hours because engineers had not moved the boats up in time.

x.   The 3rd Battalion, 143rd Infantry, using smoke as concealment, succeeded in crossing all its rifle companies by 1830 hours. Engineers constructed a footbridge, allowing some heavy crew-served weapons to cross. The 2nd Battalion began crossing the river behind the 1st Battalion. Companies E and F of the 2nd Battalion crossed but had to dig in 500 yards from the river. At this point, LTC Ralph J. Butcher, the US II Corps operations officer, violated the standing operating procedure (SOP). LTC Butcher decided to install bailey bridges despite enemy small-arms fire in the area. Normally, engineers emplace pontoon bridges on the heels of an assault crossing when the crossing site is secured. The engineers started construction on the bailey bridges but none of the bridges were completed due to enemy small-arms fire. The 1st Battalion started its assault at 1600 hours. By 1835 hours, A and B Companies were across the river, but C Company did not make it across until midnight. The engineers erected footbridges by midnight, but the bridges only served to permit men to straggle back to the near shore on one excuse or another. Unable to advance more than 200 yards from the river, the 143rd Infantry suffered heavy losses. The battered regiment withdrew to the near shore on the afternoon of 22 January.

y.   North of Saint Angelo, the 141st Infantry launched its second attack at 2100 hours on 21 January. Only a few boats remained. Part of F Company, 2nd Battalion crossed and knocked out the immediate enemy machine-gun positions and other direct fires. By 0200 hours, engineers built two footbridges across the river allowing the rest of the 2nd Battalion and the 3rd Battalion to cross by dawn. The two battalions dug in after advancing only 1,000 yards and suffering heavy losses. Meanwhile, the river washed away or German fire destroyed the footbridges. At daylight the German artillery fire became more destructive. By early afternoon, German fire killed or wounded every commander on the exit side except one. It destroyed all the boats. The infantrymen on the exit side were isolated and leaderless. The fighting finally stopped at 2000 hours. About 40 men made it back to the near shore. The rest were either killed, wounded, or captured.

z.   The Germans defeated the 36th Division. The division lost 1,681 soldiers in the two regiments that tried to cross the Rapido River. Attached units suffered several hundred additional losses. The Germans took 500 American prisoners during the two-day battle. The Germans suffered few losses and held their positions along the river.

1-2. Reasons for Failure. The 36th Division's river-crossing operation failed for numerous reasons.

a.   The division ignored the six river-crossing fundamentals:

    • The division did not achieve the most important fundamental of surprise. The German 15th Panzer Grenadier Division, alerted by the nearby British attack, awaited the attack in prepared positions.
    • The division did not conduct extensive preparations before its attack. The deception plan failed. One regiment did not conduct a rehearsal. The other regiment conducted only one rehearsal.
    • The division did not have a flexible plan. They marked no alternate approaches or lateral routes. They did not stockpile reserve engineer equipment to replace losses or open alternate crossing sites.
    • The division did not maintain traffic control during the initial crossings. The engineers guiding the infantry became lost.
    • The division lacked an adequate crossing organization. The division had no military police (MP) units for traffic control. The artillery was ineffective in destroying German artillery. The division also lacked reserves to exploit the initial attack. The 142nd Infantry did not take part in the battle. The initial assault regiments, when stopped by German fire, had no follow-on forces to continue the crossing.
    • The division lacked the necessary speed to concentrate superior combat power at decisive points before the Germans could. Once across the river, the attack stopped. The leadership took no extraordinary measures to speed up the forward movement of troops to decisive points. Instead, their units dug in along the river in unfavorable positions.

b.   In addition, their crossing attempt failed because of the following specific reasons:

    • Control of the near bank was never complete. German patrols operated in the area and their artillery fire covered the areas.
    • Poor selection of crossing sites and poor preparation of approaches to the crossing sites, including mine clearance, made movement difficult.
    • Their inability to erect vehicular bridges.
    • The vulnerability of pneumatic floats to small-arms fires.
    • Their failure to follow the fundamentals of crossing on a wide front with many crossing sites.
    • Reduced effectiveness of artillery support. The overuse of smoke hampered forward observers.
    • Superior German positions integrated obstacles with direct and indirect fires.
    • Poor infantry-engineer coordination due to the lack of complete rehearsals.
    • Lack of detailed, prior planning. This led to an abnormal amount of changes with corresponding confusion.
    • Deviation from the tactical plan. This required the British 46th Division to secure the left flank before the 36th Division attacked.
    • A last-minute change by the corps operations officer to erect bailey bridges. This change came too late and only added to the confusion.
    • Darkness, fog, and smoke concealed the German positions.
    • Failure to mark lanes properly. This caused engineers to lose their way and lead troops into minefields.
    • The combination of factors that produced low morale, incomplete coordination, and hesitant action of engineers and infantrymen.
    • Too many troops were taking part in their first action while under fire.

This lesson described the fundamentals of river-crossing operations. Specifically, it outlined the—

    • Three types of river crossings (hasty, deliberate, and retrograde).
    • Six river-crossing fundamentals (surprise, extensive preparation, a flexible plan, traffic control, organization, and speed).

Failure to follow the six river-crossing fundamentals leads to defeat as shown during the failed crossing of the Rapido River.


Lesson 1 Practice Exercise:
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