"Belgium Put the Kibosh on the Kaiser" was a popular British patriotic song of the First World War.
[1] The song refers to the 1914 campaign in Belgium when the small British Expeditionary Force, along with an unexpectedly fierce Belgian defence, managed to delay the much larger German army, slowing them and wrecking the Schlieffen Plan which depended on total victory against the French to the west in a matter of weeks.
[2] By attacking Belgium, they had violated that nation's neutrality and brought the British Empire into the war because of a pledge to uphold Belgian independence.
He'll have to go to school again And learn his geography, He quite forgot Britannia And the hands across the sea, Australia and Canada, the Russian and the Jap, And England looked so small He couldn't see her on the map.
For Belgium put the kibosh on the Kaiser; Europe took the stick and made him sore; We shall shout with victory's joy, Hold your hand out, naughty boy, You must never play at soldiers any more.