British officers were ending their careers rather than accept theoretical orders to go against the Unionists, and
Good riddance for them. Its not like half of army resigned.
If it did, London would do double take at half of its army mutinying and not pass Home Rule in the first place.
The fact that overwhelming force and executions failed to work OTL (see 1916), or, for that matter, the failure of the Amritsar massacre itself to calm India, and
Executions were against Radical Irish Nationalists, not against northern unionists. Executions would not scare nationalists, who already saw London as their enemy, into surrendering. Far less punitive measures would convince Unionists,
who though London was on their side, that it was
not, and that they were alone.
That the Unionists (who were Irish themselves, I hasten to point out) had ample opportunity to recognize the Nationalists were not baby-killing papists, and the Nationalists had ample opportunity to recognize the Unionists may have had legitimate grievances, and both failed to do so OTL, and
Nationalists did recognise that Unionists had grievances. All-For-Ireland League was arguing for considerate privileges to Ulster, including giving Northern MPs
veto in Dublin Assembly, and their own separate officials in the North. And remember, Ulster counties were to be excluded from Home rule for couple years. If Unionists living south of Ulster were not abused by Dublin Nationalists, it would be obvious than neither would be northern, more numerous Unionists.
Merely getting the Home Rule Bill passed required a constitutional crisis and stripping the House of Lords of their power to block legislation, The argument is that after a little bit of bloodshed by Stalwart and Faithful British Soldiers (themselves in no small part natives of Ireland) who would march precisely as told, everything would be fine?
Bloodshed would be used only in response to bloodshed. If Ulster is
literally revolting, (and that's a big if) of course British soldiers would shoot at rebels who shoot at them. And Ulster leadership knew it, that's why they'd only try passive resistance, which would be as good as no resistance.
I reiterate that I find the position offered difficult to believe and would demand some sort of supporting evidence.
Virtual History Alternatives And Counterfactuals by Niall Ferguson has some pretty good arguments.
Let me get one thing clear. Are arguing that Ulster would risen in
violent revolt? Not just campaign of passive resistance against Dublin government? And that British army would mutiny and join them?