As to our ports, we are not in a position of force, either military or otherwise, to drive the enemy from our ports. We have not – those on whom the responsibility has been for doing such things – we have not been able to drive the enemy from anything  but from a fairly good-sized police barracks. 
We have suffered a defeat.”
Richard Mulcahy TD.
Chief of Staff
Irish Republican Army
22 January 1922 in Dail Eireann.
Mulcahy outranked Michael Collins in the IRA.
Arthur Griffith acclaimed Collins as “The Man Who Won The War.”
It seems to me that if Ireland had militarily defeated Britain Lloyd George and Churchill might have  come to Dublin to submit to the demands of de Valera, Collins and Mulcahy
But I’m neither a statesman nor a military expert and can only give a layman’s opinion.