On 17 January 1944, the British X Corps crossed the Garigliano River as part of Gen. Mark Clark’s US 5th Army offensive to seize Monte Cassino and crack the German Gustav Line across Italy. Clark didn’t expect the offensive to succeed which included not only the British but also American and French corps further north along the Rapido River. Privately, he said the best he could hope for was to pull German reserves away from the impending landings up the Italian coast at Anzio and Nettuno. The stated objective of the British X Corps’ dangerous river assault was to seize high ground that overlooked the US II Corps’ future river crossing at San Angelo. The British X Corps was initially successful and held a tenuous bridgehead over the Garigliano.
On 19 January 1944, the British 46th Division assaulted across the Gargliano River near its junction with the Liri River in support of the rest of the British X Corps. But the operation failed and even if it succeeded, it wasn’t enough to secure the lodgment. The British commander requested more troops, but Clark refused: the only available troops were the nearby US troops earmarked for the Rapido River crossing on the 20th, and Clark refused to alter the plan. Instead of crossing the river and securing and expanding the British bridgehead, the US II Corps was condemned to its own suicidal river crossing just a bit farther north. After three brutal days successfully defending against incessant German counterattacks in the rainy and cold Italian winter, German reserves from Rome finally forced the exhausted and overwhelmed British X Corps back across the river.
Although the British river assault was successful in pulling German reserves south away from the Anzio/Nettuno landings, the US II Corps paid heavily Clark’s decision and for the British failure to secure the high ground which could observe their crossing sites. Just to the north of the British fighting to secure their bridgehead, the US II Corps, consisting of the US 45th and 36th Divisions, finished their three day rest and reorganization from the grueling six week fight during Operation Raincoat.
During the battle through the Bernhardt Line, the US II Corps took 60% casualties, and nearly 80% in the line units. Replacements arrived just in time on the 19th to participate in the 36th’s rehearsals and final preparations for their assault across the Rapido River, scheduled for the next day. Farther north, the US 34th Division and French Expeditionary Corps were preparing for their own assault across the Rapido on 22 January, the same day as Operation Shingle, the landings at Anzio and Nettuno 35 miles behind the front.
On 19 January 1944, the assault elements of Shingle, the VI Corps, which consisted the British Commando Brigade and 1st (UK) Division, and the US 3rd Infantry Division and the Ranger Force, conducted a rehearsal in the vicinity of Naples. The rehearsal was a disaster. MG John Lucas, the VI Corps commander and each of his division commanders recommended the invasion be delayed in order to conduct more training. Clark and PM Winston Churchill denied the request: the invasion craft were needed as soon as possible in England for Operation Overlord, the invasion of France scheduled for May, and there could be no delays in the Mediterranean. Operation Shingle had to happen in the third week of January at the latest or it wouldn’t happen at all.
Clark hoped the river assaults and the landings behind the German defenses would convince the Germans they were outmaneuvered and abandon the Gustav Line.