Jim, everything changed after the Easter rebels were executed.
Before that I see little evidence of anti British feeling in Ireland.

Or in the Empire, whose people, like the Irish, were very willing to fight for Britain.
Things were very different in the German African colonies where harsh rule and genocide were the inflicted on the peoples.

We have the letters of thousands of WW1 soldiers as a historical source to tell us why they volunteered. It was because they believed in the cause.