Colonel Manus Roe O’ Cahan’s Regiment of Foot

Active1641 to 1645
ConflictsIrish Confederate War
First Civil War
ColonelManus Roe O’Cahan
Area RaisedUlster
Coat Colour
Flag Colour
Flag Design
Field ArmiesMacColla 1642
Phelim O' Neill 1642
Montrose 1644-45

Ulster Irish Confederate foot forming one of the three regiments of the famous Irish Brigade fighting in Scotland during the campaigns of Montrose

Service History


  • December to January 1642: Siege of Agivey Castle


  • January: March on Dunluce Castle and join with MacColla
  • January to May: Siege of Coleraine?
  • February: Skirmish at Laney (Ballymoney)?
  • May: Battle at the Brack of Gelvin
  • June: Battle of Glenmaquin, O'Cahan rescues MacColla



  • Raised or re-organised by the Earl of Antrim in Ulster
  • June: Shipped from Waterford to Scotland
  • July: Land at Morvern (7th)
  • July: Siege of Kinlochaline Castle
  • 1st September: Battle of Tippermuir - 400 men
  • 13th September: Battle of Aberdeen - 400 men
  • October: Battle of Fyvie
  • December: Raid on Inverary


  • 2nd February: Battle of Inverlochy - 200 men
  • March: Captain John Mortimer’s Troop of Dragoons formed from the regiment
  • April: Attack Dundee (det)
  • May: Battle of Auldearn
  • July: Battle of Alford
  • August: Battle of Kilsyth
  • September: Battle of Philiphaugh most of the surviving Irish executed, O'Cahan hanged at Edinburgh
  • December: Siege of Inverness, as Montrose's foot guard, led by Ensign MacDermott


There are histories of O'Cahan's regiment available online through Wikipedia and Scotwars

The deposition of Brian Modder McHenry O'Cahan states that “On or about 5th or 6th January 1642, Irish forces under command of James McColl McDonnell, John Mortimer, Colonel Manus Roe O'Cahan, Gilduffe O'Cahan and Brian Modder McHenry marched on the town and castle of Dunluce … .”

An account of the Brack of Gelvin is available online at 'One Effort More' via the Wayback Machine

It's not confirmed that O'Cahan's were present at the siege of Coleraine and the fight at Laney, but it seems probable the force stayed together with MacColla. Their presence at Glenmaquin does seem likely as O'Cahan was present himself.

Whether the regiment the Earl of Antrim sent to Scotland was really a continuation of O'Cahan's regiment in Ireland is a question for further discussion. If so there had certainly been many changes of officers, with the regiment perhaps benefiting from Irish veterans of the Continental wars brought back by Owen Roe O'Neill.

By Philiphaugh, O'Cahan commanded a composite battalion made up of all three regiments of the Irish brigade.

Shown below is a history of O' Cahan's regiment kindly provided by Richard Frank:


Following the rebellion in Ireland in 1641, Randal MacDonald, Earl of Antrim, raised a regiment of foot, under his steward, Archibald Stewart, to guard his estates (see the Earl of Antrim’s Regiment of Foot ). His was an uneasy situation, as he was loyal to the King and a marked man as far as the Earl of Argyle and the Covenanters were concerned. His tenants, clan and feudal followers, though, included both Catholics and Protestants from three sources: Ulster Protestants (mostly Lowland Scots by descent); Ulster Catholics and refugees from Campbell expansion in the West Highlands and islands.

To accommodate this dilemma, the regiment had seven companies: five being comprised of Protestants, whilst those Catholics whom the Earl trusted were recruited into two companies; one being commanded by Turlough Og O’Cahan (the son of the Earl’s foster brother, Ghiolla Dubh O’Cahan) and the other by Alasdair MacDonald, a younger son of Coll “Keitach” MacDonald of Colonsay.

As tales of massacres and atrocities poured in, tension increased along the sectarian divide in the regiment. Colonel Stewart decided to attack a regiment of Antrim Catholics led by Turlough’s brother, Manus Roe O’Cahan, who were besieging Agivey Castle in County Derry. Stewart seems to have planned to disarm and incarcerate or slaughter the two Catholic companies before he did this.

On 2nd January 1642, the two Catholic companies marched, with banners displayed, on the remainder of the regiment, as it lay quartered at Portnaw. They gave a volley of musketry then charged. After a few minutes of confused fighting, Stewart’s men were put to flight with the loss of about eighty killed. Once the regiment was dispersed, the local Catholics crossed the Bann and informed the insurgents. Hundreds of rebels re-crossed the river including some of Manus O’Cahan’s men and a force under the Scot, Captain John Mortimer. Local MacDonalds and O’Cahans rose to join them. These sources were the genesis of O’Cahan’s regiment and the rest of the Irish Brigade. Interestingly, Major Christopher Ledwich’s Company of O’Cahan’s contained many Englishmen {possibly some of them experienced professional soldiers from European wars.}

On 11th February, Stewart led a sortie from his base in Coleraine. His force of around 1,100 men spotted some rebels near Ballymoney. Pursuing them, Stewart & Co. were drawn into the boggy ground in the area known as the Laney. An ambush had been set by Alasdair with around 700 men. Alasdair commanded his troops to ‘lay down all their fyre-arms’ [having fired them] ‘fell in amongst them with swords and durcks.’ Stewart lost between 600 and 900 men. This fight - sometimes known as the battle of Bendooragh - is considered by some scholars to be the first example of the Highland Charge, which was so formidably used in the War of the Three Kingdoms and subsequently in the Jacobite risings.

Manus O’Cahan’s regiment, recruited for Antrim’s expedition to Scotland in support of King Charles, landed in Morvern on 7th July 1644, four hundred strong, and took Kinlochaline Castle from a Campbell garrison. In little more than a year, they engaged under the Marquis of Montrose in seven general engagements, all of these except Philiphaugh being victories.

Additionally, the regiment played the principle part in the fighting at Fyvie on 28th October. Montrose was taken by surprise by the appearance of a Covenanting army commanded by Argyle and the musketeers of O’Cahan’s had to attack Covenanters with cold steel to obtain powder for their weapons ( legend has it that the shot was quickly provided by melting down a variety of pewter domestic utensils from the castle and palace - including chamber pots. ) Christopher Ledwich, the original Major of the regiment, was among those killed.

In the course of the campaign, musketeers were mounted on captured horses, to provide dragoons for scouting, raiding and to supplement the cavalry. Captain Mortimer’s company of O’Cahan’s supported Nat Gordon’s troop of horse at the Battle of Aberdeen and seems to have provided the dragoons of Montrose’s army. This unit were the ‘troop of Irish dragoons’ famous for ‘marching doon through Fyvie-o’ in the song.

When Alasdair parted from Montrose in the Summer of 1645, he left 500 troops with his general. O’Cahan’s regiment formed the bulk of this force, with Thomas Lachtnan or O’Lachlan ( formerly the Major of Antrim’s brother, Alexander MacDonald’s regiment ) as second in command. David Leslie attacked the Royalists at Philiphaugh at dawn on 13th September with an army which outnumbered Montrose’s effectives by nearly ten to one. The foot fought heroically for some time but, after losing 200 casualties and the few cavalry having been forced from the field, the bulk of the survivors surrendered on terms. More than a hundred of these were shot at the urging of Covenanting ministers and some 300 women and children following the regiment were barbarously massacred by Leslie’s soldiers and the local country people. O’Cahan and Lachtnan were later hanged from the south wall of Edinburgh Castle.

When Montrose re-assembled his forces in the Highlands, it was found that Ensign MacDermott of O’Cahan’s had fought his way off the battlefield with the royal infantry standard. The survivors of the unit were incorporated into a foot guard for the Marquis, under MacDermott’s command.

Richard J. Frank 2020

Coats, Flags & Equipment

Notable Officers

Manus Roe O’ Cahan

Donnoughue O’ Cahan

Lieutenant Colonel, led the regiment at Tippermuir, Aberdeen and Fyvie.

Officer Lists

Brack of Gelvin 1642

  • Col. Manus Roe O’Cahan 200
  • Capt Brian O’Cahan 300
  • Capt Aveny McGory 100
  • Capt Galleglasse O’Cahan 100
  • Capt Rory Rent O’Cahan 150
  • Gory O’Cahan 100
  • Brian Carragh 150
  • Caul O’Neale 150
  • Con O’Gormley 100

(note: some companies may not have been formally part of the regiment.)

O'Cahan's in Scotland

Ormond papers in the National Library of Ireland entitled “List of men gone unto the Isles. Sent by the Lord of Antrim to my Lord Ormonde, 15 Nov. 1644”:

A breefe note of Collonell O Cahan's regiment:

  • Collonnell Cahan's own company consisting of 100 men complete.
  • Officers Lieftennant Cnogher O Cahan, Ancient Dualtagh Mac Duffy
  • Sargeants of the company Owen O Cognoghor and Hugh Mac Cormacke
  • Lieftennant Collonnell Donnaghe O Cahan's company consisting of 100 men complete.
  • Officers Lieftennant Shane O Cahan, Ancient John Cooper
  • Sarjeants of the company Bryen Oge Mac Cormacke and William Oge Mac Cormacke
  • Sarjeant-Major Ledwitch his company consisting of 100 men complete.
  • Officers Lieftennant James Dease, Ancient Bartholomew Newgent
  • Sarjeants of the company Tohill Moddirrt Mac Illrey and John That.
  • Captain Art O Neale's company consisting of 100 men complete.
  • Officers Lieftennant Con O Neale, Ancient Bryen O Neale
  • Serjeants Hugh Oge Lavery and Hary O Muldowne
  • Captain John Mortimer's company consisting of 50 men complete.
  • Officers Patricke O Mallen, Lieftennant Phelim O Donnelly,
  • Ancient Daniel Mac Duffy and James O Mulhollan, Sargeants.
  • Captain Rowry Duffe O Cahan's company consisting of 50 men complete.
  • Officers John Mac Guyer, Lieftenant Donnagh O Cahan,
  • Ancient Edward Keltey and Terlagh Mac Cana, Serjeant .

In all, 500 besydes officers


  • 1642: 1350 allegedly at the Brack of Gelvin
  • 1644: 500 besides officers sent to Scotland

See Also