clipped from: www.firstworldwar.com   
Britain entered the war on 4 August 1914.  The possessor of a small professional army and without a policy of conscription she had urgent need of more men - many, many more men - for training within the British Expeditionary Force (BEF).
David Lloyd George

Thus the government in London acted quickly in bringing out a stream of recruitment posters, including possibly the most famous of its type, featuring Lord Kitchener ("Your Country Wants You!").

Other posters followed in due course, many urging wartime economy.  Others simply encouraged continued support for government policy, usually by whipping up indignation against the latest alleged outrages committed (invariably) by the German Army.

There are five pages of British posters available.  This is page one.  Go to page 2, page 3, page 4 or page 5.

How the Hun Hates!
Once a German - Always a German
The Hun and the Home
Red Cross or Iron Cross
It is Far Better to Face the Bullets
Who's Absent?  Is it You?
Daddy, What did YOU do in the Great War?
Your Country's Call