As any battlefield pilgrim can tell, there have been no closer comrades-in-arms than the soldiers of Britain, Canada, Australia, and New Zealand. When the Great War broke out, the three dominions all pledged to stand behind the mother country, in Australia’s case, to the last man and the last shilling. Four Canadian, five Australian, and one New Zealand division became the shock troops of the British army, and generals John Monash and Arthur Currie were among the war’s most acclaimed commanders. 67,000 Canadians, 60,000 Australians, and 16,000 New Zealanders (along with nearly 900,000 Britons) proved with their lives their countries’…