Imperial Service

The Territorial Force (T.F.) were not liable for overseas service. 
In time of national emergency, the troops of the regular army would leave for service overseas, and in their place, responsibility for Home Defence would fall to the men of the Territorial Force.
The Government however, realised that with the larger conscription-generated armies amassing on the continent, that should a war come and the Army be called to Europe, that a reserve would be needed to supplement them and provide a pool of trained men to go and fight. Thus, in 1912, The "Imperial Service Obligation" was introduced for the T.F. 
By signing Army Form E.624, the T.F. soldier agreed to “subject himself to liability to serve in any place outside the United Kingdom in the event of National emergency.”  It was a voluntary undertaking on the part of the Territorial Soldier, and in nearly every case, entire units signed-up to a man, to serve overseas if the need arose.
In compensation, the volunteer received a white metal brooch bearing the words “IMPERIAL SERVICE” which he could wear above the right hand pocket of his service dress jacket, just like Sergeant Sydney Green, above, of 4th Suffolk whose badge can be seen above.

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