The Administration of Exchange

On the night of 24th - 25th July 1917, 9th Suffolk were relieved in the front line near Arras by the 6th Sherwood Foresters.
Though the exchange of positions passed uneventfully, the administration of handing over the front line from one unit to another was a massive administrative undertaking, which the Adjutant was expected to perform every time the Battalion entered or left their positions.
The change over was usually preempted by a visit form the relieving Battalion. In this case, a party of the CO and all Company Commanders of the 6th Sherwoods, arrived late on the afternoon of the 23rd to check over their new positions. "The Coy. Commanders and 1 N.C.O. per Company will remain with the Coy's until relief" wrote instructions in the War Diary.
For those leaving the trenches, in this case, 9th Suffolk, they had to provide "Tunnel Warders" to assist the new Battalion in reaching the front safely and securely through the maze of tunnels that linked the front line to the rear areas in Arras. In advance to this, plans were already be enacted to ensure that those leaving the line, had sufficient billets to return to. "A Billeting Party" continued the War Diary "consisting of the Quartermaster and 4. C.Q.M.Sgts. and Sgt. Dent will report to the Secretary MAIRIE (Town Hall) by 24th inst., and will await Battalion."
Back in the front line, everything the Battalion were leaving behind for the relieving Battalion, had to be checked and indented for, "All trench stores, S.A.A. (Small Arms Ammunition), grenades, etc., in line; secret maps, photographs, defines schemes and documents dealing with the area will be handed over. Receipts will be forwarded to the Orderly Room by 10. a.m. 25th inst. 3 Trench Store cards attached. One to be forwarded to Adjutant by 12 noon 24th inst., one handed over, and one as above. Great care must be taken in the checking and listing of all stores."
The instructions continued as to the loading and checking of officers kit, the caretaker left in charge of it, the allotted lorry for extra kit, its rendezvous with the Battalion, and the route it would take. Strict discipline was to be observed by the Battalion Transport Officer, special points being noted as; "no overloading, no unauthorised personnel with the transport. Any parties accompanying the transport will be marched in formed bodies properly armed and equipped." The detailed instructions continued; "All cooking utensils and Coy. store now in trenches, will be sent down to transport on the night of 23/24th inst. the minimum of officers kit and messing to be retained." Finally perhaps was the most important and final item onto list was; "Relief complete to be wired to Battalion Headquarters by B.A.B. code." 
"BAB" codes were contained in the pocket manual "S.S.524 - Trench Codes" The booklet detailed a series of short, usually 3 digit codes to signify important events. Introduced in May 1917, the code could be transmitted using the now commonplace "Fullerphone" - a device that could transmit and receive messages via either telephone to morse key. It interrupted the harsh signals of field communications that had to be earthed to be transmitted, into a softer tone. All earthed communications could be read by the enemy if he had sufficient listening apparatus, but by muffling the signal, it became harder to read. By adding a code, it became virtually impossible. However, like the Enigma machine that followed in the Second World War, the operator at the other also needed S.S.524 to understand and decode the message.

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