During the early part of the war a number of Manchester Regiment soldiers were transfered to the Rifle Brigade, In this article by Andy Pay, historian of the Rifle Brigade, he explains the circunstances and it's history
In response to Lord Roberts appeal, the National Reserve was formed in the years just before the war. Every man with previous military service of any kind was eligible, and all who enrolled undertook an honourable obligation to serve in the event of a war. Thus in August 1914 large numbers of old soldiers joined up throughout the country.
At first their duties were ill defined. They were not uniformed or armed and they began by combining with the Police in guarding railways, bridges and such vulnerable points, in anticipation of sabotage which, in any event, was frustrated by the very efficient round up of German agents on the outbreak of war.
Gradually the duties of the National Reservists became more military. They were recognised by the War Office on 17th August 1914, and on 22nd August were attested and appointed to Home Defence Companies which were supernumerary to the eight service companies of their local Territorial Battalions.
This was not an ideal one, and as the Territorials Divisions moved from their peace stations to the theatres of war, these companies, with no higher organisation, were scattered throughout the kingdom. They were far too numerous for the prospective duties required, for by this time it was clear that the War would not be fought on this side of the Channel, they also included a large number of those who were capable of playing more active parts.
Thus it was that on 29th July 1915 the War Office decided to concentrate a number of these companies at Halton Park, near Tring, and form them into Garrison Battalions, withdrawing all fit men and sending those unfit to existing Home Service Provisional Battalions.
As mentioned previously, the seven battalions of these Garrison troops formed and recognised in December 1915 were lumped under the Rifle Brigade banner as the only three regiments at this time that had no Territorials were the Guards, K.R.R.C., and the Rifle Brigade.
Their record and Pay office were seperate from the R.B.'s they just had the R.B. name, hence the mass of these Territorials became R.B.'s simply as the head of recruitment of the day suggested these seven battalions were put under the R.B. banner.