You've just stumbled on one of the great political controversies of Canadian history, and it's one that demonstrates a lot about the divide between French and English citizens in Canada. One could argue that the two most important things about the First World War for Canada were the death toll, and the fallout from the conscription controversy.

Firstly, why didn't French Canadians care enough about the invasion of France to risk their lives over it? This justification was used to try and rouse French Canadian support to a small degree - for example there was this propaganda poster that tried to call on cultural solidarity - but the reality is that France and Canada were set on two totally different paths when Britain won the Seven Years' War (a conflict interlinked with the "French and Indian War", so if you're from the states you might be more familiar with that name). A British army under General Wolfe took over Quebec City, things went badly for France in other theatres, and so the war ended in 1763. France abandoned its northern colony in exchange for keeping power over a sugar-producing island - a much more profitable prospect - in the Treaty of Paris.

So by 1914, a lot had passed on both sides of the Atlantic. During the 155 years since Quebec City was taken by the British, France had experienced a revolution which altered its religious culture while the influence of the Church in Quebec remained pretty strong as British rulers reached an accommodation with clergy after the Conquest. France had become a more urban, metropolitan place. Meanwhile Quebec was comparatively underdeveloped, and French Canadians were systematically excluded from places of prominence in business by an Anglo elite, even in Quebec. Most importantly, relatively few French Canadians still had close relatives in France, because many French Canadians descended from people who had moved to the colonies in the 17th or 18th centuries (indeed, it's legendary that most Quebecers can tie their descent back to one of the Filles du Roi who arrived from 1663 - 1673).

Contrast this to the situation in English Canada. Most immigration to Canada in the era of the First World War was from Britain and the United States, as a matter of government policies that gave easier admission to these Anglo populations. The prior government had recently encouraged a large wave of immigration to re-populate the prairies - so there were a tonne of people newly arrived from Britain living in Canada as of 1914.

A full 70% of Canadian soldiers during the First World War were born in Britain (and thus most had family back there, memories, social ties). That's a lot more concrete and motivating than just having a language in common.

This explains why the politics of the war was totally based around the British Empire. Canada was immediately entered into the war when Britain declared war in 1914, because it was a colonial dominion without foreign policy independence. English-Canadian politicians and pro-war voices emphasized how Canada was coming to the aid of the empire. Everyone from parliamentarians, to the militia leader turned Expeditionary Force organizer Sam Hughes, to the clergy of the Church of England in Canada, to propaganda emphasized the imperial duty. It didn't help that Hughes and many of those politicians were pretty anti-Quebec.

So if the reason Canada was involved and the main motivation of the biggest pro-war voices was all about the British Empire, then French Canadian Nationalists had an inherent reason to oppose their own participation in it. This nationalist movment was only nascent, but it had prominent places in the press. For example, Henri Bourassa was the most prominent of these nationalists. He ran a newspaper called "Le Devoir" and was a member of Parliament at the time of the war, so he acted as a voice for anti-conscription politics on the national stage. He argued that Canada should concentrate on its own development and grow towards independence from Britain.

Conscription was not immediately imposed, as a flood of mostly British volunteers headed to enlistment offices throughout 1914 and 1915. However, Canada suffered heavy losses during the Battles of Ypres and the Somme, meaning that numbers of soldiers needed to be replenished. Prime Minister Borden, leader of the Conservative Party, felt increasing pressure from military officials and British leaders to pull the trigger on conscription. After a visit to the front lines and attending the Imperial War Conference in May 1917, Borden proposed the Military Service Act, which would require conscription.

Borden decided the best way to lead Canada into conscription was to create a union of different political parties so that Parliament would be well, united, around the issue. However, his main opponent, Sir Wilfrid Laurier, refused because his Quebec constituents would not agree to conscription and his agreement would only encourage them to support nationalists like Bourassa. Canada entered into an election campaign, in which politics were totally divided based on language - English Canadians in Parliament almost all ran under Borden's Union Government banner, whether they had been part of the Borden's Conservative Party or Laurier's Liberal Party before the conscription issue. The Union Party was essentially running against a mostly-French Canadian remainder of the Liberal Party and the Labour Party, a third party which represented mostly union members and left-wingers (who mostly opposed conscription on other grounds).

The Union government won in a landslide. This is the electoral map. You'll notice that literally every province and territory voted massively in favour of the Union government, except for Quebec which voted overwhelmingly for the Liberals and PEI was split down the middle between the Union and Labour. Taking this as a mandate from the majority of Canadians, the newly-elected 13th Parliament immediately passed the Military Service Act. Predictably, this led to several days' rioting over Easter 1918 in Quebec City when police attempted to arrest draft dodgers, and as many as 150 people were injured.

This wasn't really the end of it. The question of conscription came up again during the Second World War for very, very similar reasons. The First World War crisis also served as a reminder and symbol of the fundamental differences between French and English Canada.

If you'd like to read more about it, maybe you could check out Granatstein's "Broken Promises: a history of conscription in Canada." I haven't finished it but the historian is usually quite readable and based on the intro and chapter beginnings, seems like it provides a solid outline that should fill in a lot of the blanks for you. If you're looking for something short and easy to find, the Canadian War Museum has an interactive site about conscription and other Canadian war histories here.