As I have often noted on this site, the American Civil War is the only conflict in the Irish experience which compares with World War One in terms of scale. But just how many Irish served during the conflict? Relatively little detailed modern research has taken place to establish this, and it is undoubtedly a topic that is in need of substantial examination. In an effort to move towards a more accurate number I have examined some of the most recent figures presented by scholars examining specific forces and arms of service, and combined these with (I hope) reasonable extrapolations for the remainder of the military. The results suggest that Irish-born numbers were substantially greater than is often assumed, and that the figures are a lot more comparable with those of World War One than we might think.

Attempting to accurately (in so far as is possible) examine the number of Irish-born men who served in the American Civil War has been a longstanding goal. I am far from the first to look at this, and indeed it is a topic that has been raised a number of times on the site. I must particularly acknowledge the efforts to highlight this issue by blogger Lisdoon Varna, who has drawn attention to the potential underestimation of Irish numbers in this post on his own blog, and suggested alternative figures. The nature of the records kept during the American Civil War means that we will never be able to go beyond estimates for the total number of Irish in service, but there is no escaping the need for a detailed and thorough examination into establishing figures for Irish involvement. This post is primarily intended to highlight a potential need to raise our estimates, and to stimulate discussion and debate. Each of the headings below explores one aspect of the issue surrounding the total numbers of Irish-born men, with each of the resultant figures being brought together at the end of the post to put forward a suggested total. It is my view that this figure is in all likelihood relatively accurate.

Irish in the Confederacy

We are fortunate that Professor David Gleeson has recently undertaken the most detailed review of the Irish in the Confederacy yet produced, which includes an attempt to accurately estimate the numbers of Irish who served the South during the war. The figure he arrives at is c. 20,000 men; although dwarfed in comparison to Irish service in the Federal forces, such a total would in fact represent the enlistment of just over 50% of those Irishmen of military age in the South, a proportion which significantly exceeds that seen in the North. (1)

Irish in the Union- The Current Figures

Given the fact that the overwhelming majority of Irish served the North during the war, it is no surprise that the key to putting forward a total figure is fundamentally a question of how many Irish served in the Union forces. The most commonly cited figure here is c. 150,000; this is the number I give in my own publication Irish in the American Civil War and it is put forward in numerous other works which address the topic. Some make clear the important distinction that this is a figure for the Union army, rather than the Union forces as a whole. Crucially however, it is often the case that the figure of 150,000 is incorrectly cited as representing the total number of Irish who fought for the North, rather than just in the army. In fact, the figure of 150,000 not only underestimates the total number of Irish who fought for the Union, it also underestimates the total number who served in the army. To understand why this is the case it is necessary to review the analysis on which this 150,000 figure is based. (2)

Investigations in the Military and Anthropological Statistics of American Soldiers

The figure of 150,000 Irish in the Union army has its origins in Benjamin Apthorp Gould’s Investigations in the Military and Anthropological Statistics of American Soldiers, published in 1869. This remarkable piece of work gathered together vast amounts of data relating to volunteer enlistment during the Civil War and presented the statistics under a range of themes. Interestingly, one of the central figures in gathering the information ultimately used in Gould’s work was Irishman T.J. O’Connell, a graduate of U.C.D. and Chief Clerk at the Sanitary Commission’s Statistical Bureau between 1863 and 1865. Gould arrived at a figure of 144,221 for the total number of Irish in the volunteer service during the American Civil War. The methodology he employed to achieve this (at least to the untrained eye) appears reasonable. What is significant is what he omitted. Gould clearly notes in the publication that his figure represents volunteers in the Union army from a selected number of states. It excluded members of the navy, members of the regular army (aside from those who had started service in volunteer units) and also the 92,000 volunteers from California, Oregon, Nevada, New Mexico, Utah and Washington Territory. If we accept the figure of 144,221 as a baseline, we then need to assess the potential level of Irish service among those excluded categories in order to produce a more accurate total figure for Irish participation in the war. (3)

Irish in the Union Navy

Michael Bennett has produced the best work on ordinary servicemen in the Union navy. He gives the enlistment figures in the Union navy between 1861 and 1865 as 118,044 men. As he points out, Irishmen were proportionately more numerous in the naval service when compared with the army. His statistical sample suggested that 20% of the entire Union navy were Irish-born. If we accept this, it gives us a figure of c. 23,608 Irish sailors to add to Apthorp Gould’s baseline figure. (4)

Irish Volunteers from California & the Territories

Apthorp Gould excluded these 92,000 volunteers primarily because, by and large, they did not have an active role in the major fighting theaters. However, these men did serve during the American Civil War; for example many were engaged in operations against Native American populations between 1861-65. Also a number of units from such locations had strong Irish contingents, e.g. the 3rd California Infantry. It would seem reasonable to assign a proportional figure of Irish among their ranks equal to that which Apthorp Gould found for the states he examined. His figure of 144,221 represents slightly over 7% of the total number of white volunteer soldiers he cites in his study area, namely 2,018,200. Taking 7% of the 92,000 excluded volunteers we arrive at a figure of 6,440 to be added to our total. (5)

Irish Soldiers in the Regular Army

Attempting to establish the numbers of Irish in the regular army during the American Civil War is more difficult (I would be pleased to hear from any readers who are aware of research into this area). Those recruits who may have initially served in volunteer regiments before joining the regulars are presumably accounted for in Apthorp Gould’s baseline figures. Not accounted for are those Irish who were in the regular army at the start of the war and those who enlisted directly into the regulars during the conflict. What is known is that the regular army traditionally proved extremely attractive to Irishmen. For example, when the war began at Fort Sumter, South Carolina, Irish-born soldiers outnumbered those American-born within the fort. Although it almost certainly results in an underestimate of Irish numbers, it is deemed prudent to examine figures based solely on regular army numbers prior to the outbreak of the Civil War in April 1861. A total of 16,403 men were on the rolls of the regular army on 1st January 1861. It has been estimated that during the 1850s up to 60% of the regular army was made up of Irish soldiers. If, for the sake of argument, we take a figure of c. 40% Irish-born in the regulars at the start of the war, this gives us an additional figure of 6,561 men to add to our total. (6)

Irish-Americans- The Great Imponderable

Of course the one large group of ‘Irish’ that cannot be included in the total figure are those Irish-Americans not born in Ireland. This is unfortunate, as there was perhaps no war in the Irish experience where so many men not physically born in Ireland so closely identified themselves as Irish. As a result our total figure cannot include men like Peter Welsh, who’s American Civil War letters are among the most commonly cited with regard to Irish participation in the conflict (to such an extent that it is sometimes erroneously assumed he was born in Ireland); nor does it include the likes of James A. Mulligan, the Irish New Yorker who raised the 23rd Illinois ‘Irish Brigade.’ Although not everyone born into Irish-American communities regarded their Irishness as intrinsically important (Phil Sheridan would seem a case in point), there were nonetheless many thousands of men, who cannot be included in the total, who likely viewed themselves as much Irish as American.

The Irish in the American Civil War- A Revised Figure?

Where then does this leave us in terms of a total figure for Irish service in the American Civil War? A recapitulation of the figures is given in tabular format below:

Confederate 20,000
Apthorp Gould Union Volunteers 144,221
Union Navy 23,608
California & Territories Volunteers 6,440
Regular Army, April 1861 6,561
TOTAL 200,830

This suggests that the number of Irish-born men who served during the American Civil War was in excess of 200,000. Even this figure excludes some men- for example those members of militia units who served for 90 days at the beginning of the war but did not subsequently re-enlist (this would include, for example, some of the 69th New York State Militia who fought at Bull Run). Also the issue with regard to regular troops who enlisted during the conflict needs further work. This analysis is very much a preliminary estimation, designed to stimulate discussion. I am eager to hear reader’s thoughts on any and all of the proposed numbers and to hear of any other information that can be brought to bear with regard to this question.

The probability that in or around 200,000 Irish-born men (not to mention those Irish-Americans not born in Ireland) fought in the American Civil War raises interesting questions with regard to the status of the conflict’s memory in Ireland. If these figures are accurate, than the American Civil War much more closely rivals World War One as the largest conflict Irish people have experienced (in terms of numbers who served). Of course, one must remember that World War One drew on a significantly smaller relative population. This accepted, there is the potential that more Irish people from the area that now constitutes the Republic of Ireland served in the American Civil War than in World War One. For many of those counties who saw the highest levels of emigration resulting from the Famine, we can say that the American Civil War was undoubtedly the largest conflict in their people’s experience. So when we look at counties like Cork (which saw in excess of 146,000 people emigrate between 1851 and 1860), we can safely say that more Corkmen fought and more Corkmen died in the American Civil War than in any other conflict in history. Such realities make the apathy with which Ireland has treated (and continues to treat) the exploration, examination, education and remembrance of this topic all the more stark. (7)

(1) Gleeson 2013: 60. (2) Shiels 2013, for an example citing the figure of 150,000 as the number for the Irish in the Union Army, see Ural, The Harp and The Eagle, 2006: 2; (3) Gould 1869: viii, 26, 27, 2; (4) Bennett 2004: 5, 9; (5) Gould 1869: 27; (6) Newell & Shrader 2011: 3 ,Ural 2006: 33; (7) Miller 1985: 570;


Bennett, Michael J. 2004. Union Jacks: Yankee Sailors in the Civil War.

Bruce, Susannah Ural 2006. The Harp and the Eagle: Irish-American Volunteers and the Union Army, 1861- 1865.

Gleeson, David T. 2013. The Green and the Gray: The Irish in the Confederate States of America.

Gould, Benjamin Apthorp 1869. Investigations in the Military and Anthropological Statistics of American Soldiers. 

Miller, Kerby A. 1985. Emigrants and Exiles: Ireland and the Irish Exodus to North America.

Newell, Clayton R. & Shrader, Charles R. 2011. Of Duty Well and Faithfully Done: A History of the Regular Army in the Civil War.

Shiels, Damian 2013. The Irish in the American Civil War.