For Ulster Unionists generally and the thousands of men of the 36th (Ulster) Division on the Western Front the losses at the Somme amounted to a loyalist 'blood sacrifice' to match that of the insurgents who died in the 1916 Rising.
To the men of Carson's Army, the former UVF founded to resist Home Rule, and many nationalists serving in the 16th and 10th Irish divisions in 1916 the Rising was a 'stab in the back'.
While the nationalist troops feared that the insurrection might prevent the achievement of Home Rule those from a northern Protestant background were concerned for the safety of their homes and families.
The feelings of Ulster Protestants are captured in a diary that has lain unnoticed for 90 years and has now been acquired by the Public Record Office in Belfast.
The handwritten chronicle is that of a young officer in the 36th (Ulster) Division named McDowell and it shows the searing impact of the Rising on the northern-born volunteers.
Unusually the writer was not based in France but was a member of a battalion posted to the Russian Front.
In an entry in his diary for May 11 1916 the young soldier wrote: "Still freezing very hard. The Irishmen in the Brigade are hearing that there is a rebellion going on in Ireland and are very much disturbed. Several of them wanted to go home straight away."
McDowell was asked by his comrades to put the matter before their commanding officer.
So serious was the situation among the rank and file that the commander agreed to meet 50 of them informally to hear their concerns.
McDowell suggested that his superior officer should send a cable to the Unionist leader Sir Edward Carson "to find out exactly how things stood in Ireland and if Carson's reply was not reassuring, that he should send Lieutenant Smiles straightaway home to find out".
"If things were all right" the men "would be satisfied" but if they were not it was proposed to have "one squadron, composed principally of Ulstermen, sent to Ireland, if possible".
The other squadrons might remain in Russia. According to the diary, the commander readily consented and ordered Lieutenant Smiles to cable Carson "and if he did not get a reply within three days to go home and find out. The commander then went off to Petrograd".
Within five days the northern troops had been reassured by an official confirmation that the Rising had been crushed and that Ireland was in a settled condition.
The diary reads: "16 May 1916: McCausland got a wire to say that there was great damage done to Dublin by fleet-guns and a very large number of casualties."
By this stage Pearse, Connolly and the leaders of the Rising had been executed by military court-martial and martial law had been imposed on the country.
The relief of the Ulster Volunteers on the Russian front is clear from McDowell's reaction: "We are all very glad to know that Ulster had been quiet."