I came across a description of Scottish troops in the First World War as representing "The Forth Dominion". The context was a discussion of how by 1918 the shock forces of the British Empire on the Western Front came mainly from the then dominions of Canada and Australia. I can't remember which was Third Dominion, either New Zealand or South Africa. The Scots produced four infantry divisions during the war. Three, the 9th, 15th, and the 51st, served entirely on the Western Front while the fourth, the 52nd fought at Gallipoli, in the Middle East and ended the war on the Western Front. The most famous, now, was the 51st, but it wasn't long referred to as Harper's Duds for no reason. Its fighting record was spotty, though poor performances at Arras and Cambrai were down to poor leadership rather than the quality of the rank and file. And there were probably enough Scottish battalions dotted around the British Army's other divisions to form a fifth of their own. Of course Scotland was not a dominion. It had a colonial administration in the form of the Scottish Office. The fact that the dominion governments in Canada and Australia were keen to have all their soldiers serve together gave their troops a stability and cohesion which the Scottish divisions lacked as they were frequently switched from Corps to Corps. Fewer Scottish lives may have been squandered if Scotland had indeed been The Fourth Dominion.