"home rule for Ireland failed utterly to get any democratic support" That just wasn't accurate.
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The trouble is, because of the attiutude summed up in that line "take up our quarrel with the foe", that initial, naive enthusiasm for what was expected to be a short road to victory got parlayed into support for a protracted bloodbath.

The same process happened in other wars as well - typically in Vietnam and now in Iraq. And somethimg analogous happens in other situations, for example in the history of events that followed the initial Russian Revolution.