The Catholic Earl of Antrim had managed to prevent the rebellion from spreading into Antrim and north Down, remaining neutral in the early stages of the rebellion and even going so far as to raising a regiment with Protestant and Catholic companies to fight the rebels. Two Catholic company commanders, Alasdair MacColla and Tirlough O’Cahan turned on their Protestant compatriots and besieged their former commander Archibald Stewart in Coleraine but were forced to lift the siege due to a lack of artillery and the approach of the Army of Ulster.
The government’s first major expedition took place on 1-3 February with the unopposed burning of Newcastle and plunder of Naas. Later that same month, Lieutenant Colonel Monck landed with the Lord Lieutenant’s Regiment but no supplies or provisions accompanied it from England. It was soon in action taking Kilsallagan Castle north of Dublin. The besieged garrison of Coleraine was attacked while on a foraging expedition outside the city walls on 11 February in an event called ‘Black Friday.” By March the besieged Drogheda forces of Sir Henry Tichbourne had gone on the offensive taking Ardee and Dundalk and Carlingford in May. Sir Robert Stewart went on the offensive that same month in northwest Ulster turning a rebel ambush into a route at Barnesmore, capturing Strabane and routing the rebels in a battle at Glenmaquin in Donegal, thus reducing military activity of the rebels in Ulster to small unit actions.
The Scots Army of Ulster, paid for by the English Parliament, landed at Carrickfergus on 3 April and held its first muster on 7 April. The Scottish expedition sent to Ireland was initially led by Alexander Leslie, a former General in the Swedish Army, who soon departed leaving it in the hands of Sir Robert Monro, past commander of the Swedish Green Brigade and a veteran of 10 years service on the Continent. By August, all the regiments were in Ireland and occupying garrisons throughout Antrim and Derry.
In April, Ormond marched to Naas and spreading devastation on his way to Kilcullen, Athy, relieved the castles of Carlow and Cloghrenan. His column was escorting refugees back to Dublin when it was ambushed by a larger force of rebels at Kilrish, which he subsequently defeated. Coote relieved Castlegeasel and Castlejordan, capturing Trim.
The siege of Cork, garrisoned by a force under the command of Earl Inchiquin, was lifted and the castle of Limerick was besieged by the rebels.
On 27 April, Monro led a force out of Carrickfergus towards Belfast and Lisburn, incorporating Ulster settler forces enroute. He then moved south skirmishing with rebel forces storming Loughbrickland Castle as well as taking and garrisoning Newry.
As he approached Carlingford, the rebel garrison fled and Tichbourne, one of Monro’s subordinate commanders, sent a garrison to occupy it. Monro then moved back to Carrickfergus with his force divided into several smaller contingents to round up as much cattle as possible. County Down was, for the most part, subdued by this initial expedition. Monro’s operation was, as were all to follow, hampered by financial support, available supplies, an absence of improved roads, terrain that was inhospitable for cavalry and an enemy that would come and go with relative freedom striking when and where conditions made them most effective. In late May Monro marched north towards Coleraine to relieve it as well as to cut the line of retreat of the rebel forces in Antrim. On the 29 th of May he arrived at Dunluce Castle, the home of the Earl of Antrim, who Monro assumed had gone over to the rebels. This assumption may or not have been valid. Antrim was under suspicion as a result of his Catholicism and because some of his followers had joined the rebellion and were besieging Colerain and its Protestant Scots garrison. Monro arrested and imprisoned Antrim. Once the siege of Coleraine had been lifted, Monro marched east through Antrim returning to Carrickfergus, having effectively cleared Antrim of rebels.
Monro’s expedition forced the rebels into Londonderry and the Laggan Army area of operations. The rebel forces out of Antrim under the command of Alasdair MacColla and Philem O’Neil established an encampment at Glemaquin enroute to Ulster. On the morning of the 16 th of June, Sir Robert Stewart’s Laggan Army forces woke the camp with harassing fires from a small force causing a pursuit by the rebel forces into a position occupied by the Laggan main body. The efforts of Alasdair MacColla and his Antrim Scots prevented the pursuit of Philem O’Neil’s fleeing forces. Stewart then defeated a force commanded by Manus O’Cahan enroute to assisting Monro in the lifting of the siege of Coleraine. O’Cahan was captured at the siege of Dungiven not long after and sent to Derry as a prisoner.
In June the Scots under Munro moved towards the rebel headquarters at Charlemont. Finding himself low on supplies and in danger of being cut off, he retreated to Newry. From Newry, he sent raiding parties to collect rebel cattle. Indiscriminant raids in July conducted by Lord Forbes along the Munster coast complicated matters for Earl Inchiquin, the Protestant commander, threatening the neutrality of the local population. Earl Inchiquin defeated a larger force led by Barry at Liscarroll effectively making it impossible for Confederation forces to gather an army in Munster for another two years.
On 7 July the Irish Catholic Confederation met at Kilkenny electing a General Assembly and Supreme Council. All members of the Confederation took an oath of allegiance to Charles I and to uphold Catholicism. The goals of the Confederation were to reach an agreement with Charles I granting full rights to Catholics, toleration for the Catholic faith and self-government for Ireland. This was the beginning of an organized effort to conduct the war across Ireland and to move beyond the previous uncoordinated military actions.
In August Owen O’Neil arrived in Donegal with an experienced cadre of officers from the continent and was made commander of the beleaguered Confederation forces in Ulster. The following month Thomas Preston arrived at Wexford with arms and officers from the continent and was made the commander of the Confederation forces in Leinster. Both Owen O’Neil and Preston began training their forces.
On August 22 1642 Charles I raised his standard and began the First Civil War. The impact on the Army of Ulster was an immediate halt of supplies from Parliament which had agreed to supply them in a treaty with Scotland. The loyalty of the Army of Ulster’s loyalty was not an issue, but that of the Laggan Army was soon to be. David Leslie, the Earl of Leven, arrived in August as well. His arrival was followed by two expeditions under his command, the first being essentially an unopposed circuit around Ulster. The second expedition was an abortive attempt to attack Charlemont, cut short by a lack of supplies. While Leslie’s column was on its circuit, Dungannon and its settler garrison fell to the rebels in County Tyrone. One of the more peculiar events of Leslie’s time in Ulster was the brief service in the Army of Ulster of Alasdair MacColla. Leslie departed in November leaving the Army of Ulster, once more, in George Monro’s command.
Colonel Monck was sent to relieve Ballynekill in December just 18 miles from the Confederation’s headquarters at Kilkenny. He was ambushed on his return to Dublin at Timahoe by a larger force led by Thomas Preston which he easily outmaneuvered and routed. Despite Monck’s efforts, the garrison at Ballynekill surrendered to the rebels.
Throughout 1642 there were repeated efforts by Ormond and the English Parliament to order the Army of Ulster to conduct operations in the other three provinces, but to no avail. Monro was able to influence the Scottish settler forces in Antrim and Down who refused to respond to orders from Dublin or Parliament as well. It may have been possible for the Army of Ulster to put down the rebellion had it been willing and able to conduct military operations in the other three provinces.