We have all heard about how many of the soldiers on the Western Front weren't actually French / British but instead came from the colonies. What I am curious about is whether the people back in the colonies were okay with sending a bunch of troops to a conflict that presumably had little bearing on their day to day lives. To me, it seems like the opportune time for a colony to rebel or to declare independence. For example, what if Canada said "Enough is enough, we don't need Canadian troops dying to defend France, we are independent now" in 1916 - it seems to me like Great Britain wouldn't really be able to do anything about it unless they withdrew significant amounts of forces from the Western Front and sent them to Canada. This didn't happen, though. So was it patriotism that kept the colonies in line? Was it the fear of the British Navy? Would a typical New Zealander at home in 1917 approve of the war, or was there any political unrest where the colonies didn't want to send troops and material to Europe?
From the point of view of the British Empire, it’s important to note that military service on the part of colonies and dominions was mostly voluntary, and that conscription in the British homeland itself was only introduced in early 1916.
Its also important to note that the white/white ruled Dominions of Canada, Newfoundland, Australia, New Zealand, and South Africa, though not having the right to independent foreign policies, enjoyed substantial self-government and the decision to enforce military service by compulsion belonged to the local government and not Westminster.
Attempts to impose conscription did occur in Canada where the Canadian government (note, not the British government) passed the Military Service Act in January of 1918. The Act was deeply unpopular with all sections of society, but particularly inflamed resentment from French Canadians who held no loyalty to either the British Empire or France. Violent riots ensued with armed rioters and troops opening fire on each other in Quebec City. This was not however an attempt to break away from the British Empire as such.
In South Africa, the Second Boer War had ended just over a decade before the Great War started, and there was much bitterness and resentment on the part of some sections of the Afrikaans speaking white people. This spawned the Maritz Rebellion, eventually attracting around 12,000 rebels to a Commando operating in the Magaliesberg area, close to the border with modern day Botswana. The rebellion was suppressed completely by the following year, with many more Afrikaaners taking part in the suppression than the actual rebellion itself. The rebellion was however not linked to conscription. Military service overseas remained voluntary throughout.
In Ireland, an armed insurrection took place in Dublin over Easter 1916. This was again not connected to conscription, but instead an attempt to overthrow British rule in Ireland itself. There was an attempt to introduce conscription in Ireland in the spring of 1918, which galvanised Republican opinion and proved so unpopular that although the Act was passed by the Westminster government, was never actually put into effect.
In Australia, legislation made provision for conscription for home defence only. Military service overseas remained voluntary throughout. Two referendums on the matter were defeated and lead to considerable resentment and division between the opposing camps.
New Zealand was the exception with an existing compulsion to military service. Overall, about 90,000 New Zealanders served voluntarily and 30,000 were conscripted. Unlike in the other predominantly white or white ruled dominions, there was no large scale opposition to conscription.
Finally, the British Indian Army provided a very significant all-volunteer force of 140,000 men in 1914, rising to 550,000 men in 1918. This, the result of a long tradition of military service in India. British Indian Army divisions were deployed to the Western Front in 1914 and 1915, however problems existed with the infantry divisions who were unfamiliar with the latest equipment and under-supplied with artillery. Officer casualties were a serious matter as replacement had not the familiarity and experience of how to handle Indian troops. Indian cavalry units remained active on the Western Front, only being withdrawn to Egypt just before the start of the German spring offensive.
The only serious act of rebellion was the 1915 Singapore mutiny where a battalion of mainly Muslim Sepoys mutinied, attacked their officers, attempted to enrol support from German POW’s from SMS Emden and went on a 5 day rampage on the streets before being suppressed. This mutiny was again, unconnected with conscription.