The Rockenbach Report on the origins of the Tank Corps A.E.F.

“Prior to the arrival of the A.E.F., the American Military Mission in Paris had, by direction of the Chief of the War College, investigated and submitted a report under date of May 21st, 1917, giving the latest British and French technical and tactical ideas on the use of Tanks. Major Frank Parker, Liaison Officer at G.H.Q. of the French Armies of the North and North-East, submitted notes covering French Tanks in the Allied Offensive of April, 1917. In the light of our recent experience his two chief criticisms are of interest:

‘(a) Insufficient protection against fire. Little extinguishing material was provided.

(b) Faulty liaison with the Infantry. On several occasions the Tanks went ahead of the Infantry and were destroyed for lack of support. Many were destroyed.’

“The French at that time had only two types of Tanks; the St. Chaumond and the Schneider. Neither were Tanks in the sense of later development. They were more properly artillery carriers. They had to be preceded by a group of skirmishers who indicated the route for them to follow. They were bad cross-country machines; under powered; badly arranged and it was all off with the crews if they were stuck.

“A joint British and French Tank Board met in London early in May, but were unable to reconcile their ideas as to machines or tactics. The British preferred the heavy Tank to be used in advance of the Infantry and the French desired their light Tank, which they were building, to be used in close liaison with the Infantry. Their normal position to be with the battalion support and only to advance when the Infantry was held up.

“Shortly after the arrival of the Commander-in-Chief, of the A.E.F., and his staff in France in June, 1917, various committees were appointed and sent to the British and French fronts to study their organization plans and equipment. Naturally “Gattling Gun” (J.H.) Parker noted and reported on the counter to the machine gun. On July 19th, 1917, the Commander-in-Chief directed the detail of the Board of well selected officers to study the new French Tank (Renault).

“On July 28th, the Chief Ordnance Officer of the A.E.F. requested to be informed as to the number of Tanks required in order that a definite request might be made on the War Department to expedite construction. Colonel Eltinge, General Staff, in addition to his other duties, was put in charge of Tank matters.

“On September 14th, the following cablegram was sent to the War Department:


No. 159-S Paragraph 15 – for Chief of Ordnance. Careful study French and British experience with Tanks completed and will be forwarded by early mail. Project includes three hundred fifty heavy Tanks of British Mark Six pattern; twenty similar Tanks equipped for signal purposes; forty similar Tanks for supply of gasoline and oil; one hundred forty Tanks arranged to carry twenty-five soldiers or five tons of supplies; fifty similar Tanks with upper platform for field gun; total six hundred heavy Tanks. Also following Renault Tanks; ten hundred thirty for fighting purposes; one hundred thirty for supply; forty for signal purposes; total twelve hundred Renault Tanks. Replacement of Tanks requires fifteen per cent per month after arrival here. Mark Six Tanks should be in proportion of one small cannon and four machine guns and the female carries six machine guns. Renault Tanks should be in proportion of two to carry a machine gun to one to carry a six-pounder, or one carrying three-inch gun. Other material required for Tank organization includes: three hundred six-ton auto trucks each carrying complete Renault Tank; ninety three-ton auto trucks; two hundred seventy three-ton auto trucks with trailers; ninety three-ton auto trucks with kitchen trailers; ninety Ford automobiles and one hundred eighty motorcycles. Understand that arrangements can be made with Renault Works to permit manufacture of Renault Tanks in United States and that they will furnish model. Also that complete plans and specifications for British Mark Six can be obtained. These are the only models of Tanks whose use is recommended by either British or French. British Mark Six is thirty feet long and weighs about thirty tons. It is a powerful machine but limited to particular localities. Groups are assigned to particular areas for fighting. Renault is about nine feet long and weighs about six tons. It is used in conjunction with Infantry and assigned to Infantry units. Arrangements for manufacture should be made at once. Understand that French desire about two thousand Renault Tanks from United States. Will take up with French War Office later. Tanks are used in large numbers or not at all, hence shipment not expected before next Spring. Will submit recommendations regarding organization later.



“Project for Overseas Tank Corps based on 20 combat divisions, consisting of the necessary headquarters, five heavy and 20 light battalions employing 375 heavy and 1500 light fighting Tanks, was approved by the Commander-in-Chief, A.E.F. on September 23rd and sent to the War Department. Details were to be worked out and submitted later.

“On October 14th Majors Drain and Alden of the Ordnance Department were detailed by Special Order, H.A.E.F. with instruction from the Chief Ordnance Officer, A.E.F., to collect all information obtainable on the use, design, and production of Tanks. Their report, submitted on November 10th, was exhausting and interesting.

“In order to coordinate the production efforts, an Inter-Allied Tank Commission was approved and Major Drain was appointed the American member thereof. He was directed to proceed in the attempt to get an agreement with the British and French as to the best type of Tank to be constructed and coordinate the production effort so as to get the largest number of Tanks in the minimum time. The effort with the British was a success and the Anglo-American Commission decided the type of heavy Tank, which was nothing more in idea than an enlarged Renault, and started design. The French, while approving, would take no active part. On December 6th the American member of the Supreme War Council, with the approval of the Commander-in-Chief A.E.F., cabled the War Department and got approval to enter into an Inter-Allied agreement for the joint production of 1500 of the Liberty Mark VIII Tanks, and for the allotment of 1500 Liberty engines for the same. The 1500 heavy Tanks were to be produced by the 1st of October, 1918.

“In the meantime, Captain G. S. Patton, Jr., Cavalry,[1] and Lieutenant Elgin Braine, had been on duty with the French Tanks. They had thoroughly mastered the light Tank (chars d’assaut Renault). They were very enthusiastic about it and were ready to make improvements. The War Department was cabled, requesting the rapid construction of the Renault Tanks. Steps were taken to secure and send specifications and two Renault Tanks to the United States. As the Renault is manufactured by a private concern, the negotiations were slow and tedious.

“Doubts as to the usefulness of Tanks were removed by the Battle of Cambrai, starting on the 20th of November, 1917. The salient points brought out as to the value of Tanks were: Economy in men per weapon, in men per yard of front, in casualties, increased enemy’s casualties, economy in Artillery personnel, in Cavalry personnel, in ammunition and manufacture, of transportation, of labor on the battlefield, of property, of tonnage and of time.

“At Cambrai a penetration of 10,000 from a base of 12,000 yards was made in 12 hours. That the Boche counterattack left the British in worse situation than before the attack in no way diminished the usefulness of Tanks, but made clear that Tanks were not an independent arm. There must always be the Infantry to support the Tanks and secure their gains. (Cambrai was a strategical success in that it held troops away from Italy).

“This was the situation on December 23rd when I arrived at G.H.Q. and was detailed as Chief of Tank Corps.” Samuel D. Rockenbach, Chief, Tank Corps 

Excerpted from Samuel D. Rockenbach, Operations of the Tank Corps A.E.F. (Silver Spring: Dale Street Books, 2017), pp. 12-16, informally known as “The Rockenbach Report.” (Original report archived at the U.S. Army Heritage and Education Center at Carlisle, Pennsylvania under its full title,  Operations of the Tank Corps A.E.F. with the 1st American Army at St. Mihiel and in the Argonne Sept. 11th to Nov. 11th 1918 and with the British E.F. Sept. 18th to November, 1918. (France: General HQs, A.E.F., Office of the Chief of Tank Corps, 1918). OCLC Number: 25526224.))

[1] Patton was promoted in quick succession in early 1918. He had been wearing his Major clusters for only a week before he was notified that he was promoted to Lieutenant Colonel in April 1918.  Stanley P. Hirshson, “General Patton: A Soldier’s Life,” (New York: Perennial, 2003), p. 115.