This Irish song is about the rebellion on Easter of 1916. The song was written in 1919. The Irish were rebelling against the British control over Ireland in hopes to set up an Irish Republic. They thought they could overrun the British while they were in the middle of fighting the first World War. The Irish fighters were men that volunteered to do this, including the small Irish Citizen Army. The rebellion lasted 6 days. The song is all about the rebellion, telling it’s the tale of heroism and death that later led to the Irish getting full control over the vast majority of their country. 

I found the link to the song on YouTube: