"...a profound awkwardness for both of the Redmond brothers; Willie was not John, that was for certain, but he was nonetheless a Member of Parliament and his open participation in the Irish Volunteer movement spoke broadly to the way that not just volunteerism but mass political organizing had brought together Irishmen of all stripes. His murder by Ulster gunmen in Cork on August 2nd, 1915, was like a thunderclap across the island. This was the first Parliamentarian to have been killed, and for all his heightened rhetoric and radicalism compared to other members of the IPP - certainly conciliatory John Redmond - he was still one of their own, and his death seemed to portend a newer, more dangerous phase of the Civil War, in addition to so devastating poor John that he retreated into a despair that greatly diminished his influence.
Redmond's death, rather than plunging Ireland into a new round of mindless sectarian violence, represented something else instead - a bookend to the horrific communal slaughter of the past twelve months that had begun with the eerily similar assassination of Hubert Gough in Belfast, in which the violence sank instead into a lull. By the second half of 1915, all sides involved were exhausted and martial law had been extended to thirty of the thirty-two counties, enforced largely by the RIC arbitrarily depending on which community local constables belonged to; Irish Volunteers were given broad leeway in Munster and the west, while the Orange Order operated effectively unfettered under the wandering eyes of sympathetic policemen across Ulster. The disproportionately Protestant officer corps of the RIC regularly fed information to the UVF while the overwhelmingly Catholic beat policemen passed along tips on upcoming raids or arrests to the IRB and IV; Protestant officers were even occasionally assassinated by their own men. This left security across Ireland tribal but intact, to the point that despite violence being a frequent occurrence it was felt unevenly and for many barely at all. [1] The conditions on the ground for average Irishmen had drastically improved towards the end of 1915 as well. The collapse of the distillery industry due to wartime American import bans had left thousands unemployed and ripe for recruitment into the various paramilitary forces, but the mounting price crisis for food imports across Britain made farming in Ireland, at least temporarily, lucrative for many otherwise marginally employed and the increased land ownership by former tenants meant the profits of inflated grain costs did not exclusively flow to absentee landlords back in England.
More than anything, though, it was the events in India which led most in Westminster to conclude that endless escalation in Ireland was not feasible, what with new commitments needed to keep the Raj from collapsing and falling out of the Empire, and this combined with the genuine shock and grief experienced in London at the news of Willie Redmond's assassination moved many of his colleagues who had respected him. Redmond's murder in particular seemed to finally persuade Austen Chamberlain, who had been one of the most militant opponents of Home Rule within the Liberal Party and had greatly watered down Haldane's Government of Ireland Act the year before, that the status quo was untenable, and as he budged on his line of keeping Ireland with a foot inside Westminster - now coming around to a "Grattanist" solution in which Ireland would remain in a personal union with Britain a notch above the Dominions of Canada, Australia and South Africa - many of the more conservative Liberals came with their party leader. Five bullets in Cork did more for Irish liberty than five years of infighting amongst the Liberal Party to sway the intransigents.
The Nationals were beginning to desire a solution, too. Cecil, craven weathervane he may have been, was loathe to be the Prime Minister to lose Ireland and India on his watch, and as Chamberlain began to shift the Liberals towards demanding a negotiated solution in alignment with the Crown, Cecil found the political tightrope he was on increasingly difficult. The Liberals "supported" his minority government in theory but were more of a sword of Damocles over the Cecil ministry than the IPP had ever been over them, making it abundantly clear that their support was required on essentially any act of the Commons, even ones that typically did not require a confidence vote. To lose the Liberals, who had supported what Britons considered a "middle-path" course on Ireland pursued by Cecil so far to the chagrin of Ulster Unionists, would doom his government. But being too conciliatory to Irish nationalists, who had clearly won the hearts and minds of the Irish populace (particularly in the rural constituencies once attracted to Parnellism and the Plan of Campaign), was also a clear path to a permanent rift with the Ulster Unionists who already saw him as unreliable and spineless in the face of the IPP. Further complicating that matter for Cecil [2] was that Ulster Unionists were extremely unpopular with the general public, held responsible for the debacle at Curragh Barracks, for the revolt in which the Carrickfergus depot was seized, and now the murder of an Irish MP, the brother of the IPP's leader no less. [3]
Cecil was thus loathe to stick his neck out for a political solution but facts on the ground at least opened up the opportunity for his government to place their focus on India and let Ireland simmer rather than continue to boil. The public outrage on both sides of the Irish Sea over Redmond's murder made Carson blink for the moment and make clear through backchannels to UVF commanders that no more assassinations of that kind were to occur, lest the UVF lose all their public credibility. Furthermore, the internal feuds between the more radical IRB and the mainstream Irish Volunteers associated with Devlin and his AOH was exacerbated with the death of Redmond, and two organizations never known for their internal cohesion rapidly deteriorated in their coordination over September and October of 1915, with the IRB successfully curbed by the British Army's Limerick Raids in late September and the IV pivoting to pseudo-policing as a Catholic paramilitary operating in a defensive crouch to keep sectarian violence away from churches and schools, become even more a tool of Devlin than before.
What followed then was one of the strangest times of the war - the lull in violence that began in the autumn of 1915 and would carry through deep into the following year, where war didn't end but didn't get worse, and while no end was in sight it became enough of a sideshow to India that politicians in London and Dublin could take a deep breath and try to figure out how, precisely, Ireland was to extricate itself from the bloodshed. A policy of muddling along, waiting for some external event to force everyone's hand, became a sudden and disliked consensus..."
- Ireland Unfree
[1] This is materially different from how things with the RIC worked during OTL's Irish War of Independence, where they were the IRA's number one target.
[2] So things are going just great for Hugh and the Hughligans, if you can't tell.
[3] Of course it bears mentioning that Willie Redmond was to the IV what MPs like Edward Carson are to the UVF