After the Irish Rebellion starts, the rebels first attempt to move into Ulster and capture Belfast. When they meet stiff Protestant resistance in Ulster, the rebels turn their focus southward with the goal of taking Dublin. En route to attack Dublin, the rebels come upon the town of Drogheda and begin the siege of the garrison. Approximately one week after the rebels have encircled Drogheda, the English authorities in Dublin put together a relief force and send them to reinforce the Royalist strongpoint. En route to Drogheda, the English force is ambushed and routed by the rebels in Julianstown.
The English relief force is hastily put together and largely untrained. Many of the soldiers in the relief force are emaciated and sick refugees from the northern counties who are pressed into service. The detachment is commanded by Sir Patrick Wemyss and is composed of 600 foot and 50 horse. The rebel forces are led by Philip O’Reilly and Miles O’Reilly, both Irish leaders from County Cavan. Their force of 3,000 men including 300 horse has experienced commanders and appears to have been assigned to the south of Drogheda to complete the encirclement of the garrison.
On the morning of the battle, the rebels become aware of the approach of the Royalists and prepare an ambush. As the rebels spring their trap, the English commander does not immediately order his men to attack and fire upon the enemy. By mistake Wemyss orders his men to “countermarch” which causes them to move backwards as if they are retreating. The rebels take full advantage of the situation and immediately charge the Royalists. The rebel attack causes panic and confusion among the English and prevents them from coordinating an effective counter-attack. Many of the Royalists throw down their weapons and attempt to escape. The Royalist horse flee the field. In the end, the rebels kill almost all of the Royalist foot soldiers.
The victory has several short term benefits for the rebels. From the manner in which they rout the Royalists, the rebel forces gain respect as a military force. It boosts rebel morale and helps to spread the revolt throughout Ireland. For the commander of the Royal Irish Army, James Butler, Earl of Ormond, the battle shows the determination of the rebels and the degree of support for their cause. Ultimately, the Battle of Julianstown as a small part of the Irish Rebellion indirectly leads to the English Civil War and Confederate Ireland.