This battalion and its sister battalion, the 7th, were second line Territorial Army formations and comprised the 37th (Royal Sussex) Infantry Brigade, part of the 12th (Eastern) Infantry Division. These units were in France during 1940, but were not fully trained and were primarily engaged in the construction of defences, military camps and roads and the guarding of military installations in the rear areas.
In the second week of May 1940, German Army Group 'A' broke through at Sedan in the Ardennes and began their advance to the Channel ports. To meet this threat, the order was given to the G.H.Q. reserve troops of the B.E.F. to proceed to Abbeville. In the late hours of 17th May 1940, the Rifle Companies of the 6th Battalion RSR boarded a troop train at Abancourt and the Rifle Companies of the 7th Battalion RSR boarded another troop train at Buchy further down the line.
The 6th Battalion RSR train was ready to move off first but, owing to a derailment of a wagon immediately ahead, it was delayed. As a result, the train carrying the 7th Battalion RSR was diverted to the up line, thereby passing the train of its sister Battalion. The line was eventually cleared and the train carrying the 6th Battalion RSR pulled out of the station, by now some considerable distance behind the train carrying the 7th.
Around 14:00 hrs, on the 18th May 1940, the train carrying the 7th Battalion RSR stopped at St Roche station, a mile outside of Amiens. At this point, the troop train came under heavy attack from German Stukas. One bomb fell onto the engine tender and another onto the first coach which contained all the officers. The bombing of the train effectively prevented any further movement northwards and around 80 officers and men were lost.
Just after 17:00 hrs, the train bearing the 6th Battalion RSR approached St Roche station, but as an air raid was in progress, the train was stopped. When the raid had ceased, the train was switched to the up line and passed through the station. The men of the 6th Battalion RSR saw the damaged train, but did not connect it with that of their sister Battalion. Their train then proceeded into the marshalling yards.
Later the 6th Battalion RSR train started off again and it was soon discovered that the track ahead had been severely damaged and no further progress would be possible for some time. The local authorities therefore decided that the train should return through Amiens. The 6th Battalion RSR train went to Paris and then on to Nantes and St Nazaire where the men were engaged in stacking petrol and stores until 17th June, 1940. On its return to England, the 6th Battalion was employed in Home Defence duties for the rest of the war.
The fate of the 7th Battalion was altogether more tragic. The commanding officer had deployed his ill-equipped and inadequately-trained battalion in a defensive screen, in the countryside around Amiens. On the 20th May, it was their misfortune to find themselves overwhelmed and overrun by the tanks and motorised infantry of 1st Panzer Division rapidly advancing towards the coast. The Battalion was effectively wiped out in this single action.