Why did the Pro-Treaty side win the Civil War?
The Irish Civil War caused many divisions within Irish Society. The Civil War resulted from divisions within the nationalist movement as a result of the Anglo-Irish Treaty. Sinn Fein split into pro and anti-Treaty factions. The Civil War ended in May 1923 and while there was no surrender by the anti-Treaty forces, the pro-Treaty side were clearly victorious in the war. In this essay I will look at the reasons why the Pro-Treaty side won the war.
In an effort to retain the initiative in the aftermath of the Dail vote in favour of the Treaty, the anti-Treaty IRA occupied the Four Courts and other buildings in Dublin. This was a tactical error by the Irregulars as these buildings were difficult to defend and the Regulars knew exactly where their opponents were. As a result when fighting broke out up to 200 Irregular troops were killed or captured in Dublin. This significantly weakened the anti-Treaty side and contributed to their defeat.
The anti-Treaty forces lacked a coherent strategy. They were against the Treaty but different people within the anti-Treaty side were opposing the Treaty for different reasons. DeValera opposed the Treaty because of his opposition to the Oath of Allegiance to the British King. More hard-line republicans opposed the Treaty because of partition. This lack of a coherent strategy contributed to a weakening of the anti-Treaty side and the victory of the Regulars.
In contrast the pro-Treaty side had a clear objective, the implementation of the Anglo-Irish Treaty. It was an easy message for the leadership of the Regulars to get across to the general population. They argued that if the Treaty was accepted then Ireland would have Independence and the fighting would stop. This clear objective contributed to reinforcing support for the pro-Treaty forces during the Civil War.
The pro-Treaty forces had a coherent leadership. Michael Collins and Arthur Griffith played a prominent role in the military and political campaign during the Civil War. After the deaths of Collins and Griffith, William Cosgrave and Kevin O’Higgins stepped into the political leadership and Richard Mulcahy carried on where Collins had left off in the military leadership.
The anti-Treaty forces were divided. Many anti-treaty IRA commanders from the War of Independence did not join the Irregulars. There was tension between the political leadership of DeValera and the military leadership of Liam Lynch. On top of this Lynch had difficulty imposing command among the individual Irregular commanders and instilling discipline among the anti-Treaty forces. The coherent leadership of the pro-Treaty side and the lack of coherence among the anti-Treaty forces contributed to the victory of the Regulars in the Civil War.

The Regulars had significantly more resources for fighting the war. By August 1922 they had 14,000 troops and this eventually grew to an army of 60,000. The pro-Treaty side received assistance from the British government in the form of a loan of weapons and supplies and the provision of loans to fight the war. While the Irregulars had some supplies of weapons and ammunition they were lacking men and money for the war. They regularly commandeered food and other supplies turning public opinion against them. The sheer weight of numbers on the side of the pro-Treaty forces contributed significantly to the victory of the Regulars.
The Irregulars adopted the strategy of guerrilla warfare. They began to abandon towns they controlled when they were attacked, withdrawing to the countryside. However, the guerrilla campaign was less effective than during the War of Independence. Unlike the British, the Regular forces had as much knowledge of the countryside as the anti-Treaty forces. Furthermore, public support for the anti-Treaty side was much less forthcoming than during the Civil War. The election in June 1922 clearly demonstrated that a majority of the population supported the Treaty and wanted an end to the fighting. Along with this the Regulars also received the backing of the Catholic bishops who condemned the actions of the Irregulars. Lack of effectiveness of the guerrilla campaign and lack of public support for their cause contributed to the defeat of the Irregulars.
The Provisional Government were determined to defeat the anti-Treaty forces. The Public Safety Act introduced in 1923 allowed for the execution of prisoners for commandeering property, looting and arson. Seventy-seven Irregulars were executed. Some were executed in retaliation for assassination of Government supporters. The hard-line stand of the government had an impact on the outcome of the war in favour of the pro-Treaty forces.
The Civil War caused a great deal of bitterness and division that continued for decades afterwards. Large numbers were killed and it caused significant economic difficulties for the new state. Despite the loss of key political figures like Collins and Griffth, the pro-Treaty side had a more coherent strategy, were more determined and had far greater resources than the Irregulars. These factors contributed to the victory of the Regular forces in the Civil War.