Connolly has an education up to the age of about ten in the local Catholic primary school. He then leaves and works in labouring jobs. Due to economic difficulties, he joins the British Army at age 14, falsifying his age and giving his name as Reid. He serves in Ireland with the 2nd Battalion of the Royal Scots Regiment for nearly seven years, during a turbulent period in rural areas known as the Land War.
Connolly develops a deep hatred for the British Army that lasts his entire life. Upon hearing that his regiment is being transferred to India, he deserts. He meets a young woman by the name of Lillie Reynolds and they marry in April 1890, settling in Edinburgh. There, Connolly begins to get involved in the Scottish Socialist Federation, but with a young family to support, he needs a way to provide for them. He briefly establishes a cobbler‘s shop in 1895, but this fails after a few months.
By 1892 Connolly is involved in the Scottish Socialist Federation, acting as its secretary from 1895. During this time, he becomes involved with the Independent Labour Party which Keir Hardie had formed in 1893.
Connolly and his family move to Dublin, where he takes up the position of full-time secretary for the Dublin Socialist Club. At his instigation, the club quickly evolved into the Irish Socialist Republican Party (ISRP). The ISRP is regarded by many Irish historians as a party of pivotal importance in the early history of Irish socialism and republicanism.
While active as a socialist in Great Britain, Connolly is the founding editor of The Socialist newspaper and is among the founders of the Socialist Labour Party which splits from the Social Democratic Federation in 1903.
A combination of frustration with the progress of the ISRP and economic necessity causes Connolly to emigrate to the United States in September 1903. While in America he was a member of the Socialist Labor Party of America (1906), the Socialist Party of America (1909) and the Industrial Workers of the World, and founded the Irish Socialist Federation in New York, 1907.
On his return to Ireland in 1910 he is right-hand man to fellow-syndicalist James Larkin in the Irish Transport and General Workers Union. In 1913, in response to the Great Dublin Lockout, he, along with an ex-British officer, Jack White, found the Irish Citizen Army (ICA), an armed and well-trained body of labour men whose aim is to defend workers and strikers, particularly from the frequent brutality of the Dublin Metropolitan Police. He also founds the Irish Labour Party as the political wing of the Irish Trade Union Congress in 1912 and is a member of its National Executive.
When the Easter Rising begins on April 24, 1916, Connolly is Commandant of the Dublin Brigade. As the Dublin Brigade has the most substantial role in the rising, he is de facto commander-in-chief. His leadership in the Easter Rising is considered formidable. Michael Collins says of Connolly that he “would have followed him through hell.”
Connolly is sentenced to death by firing squad for his part in the rising. On May 12, 1916 he is taken by military ambulance to Royal Hospital Kilmainham, across the road from Kilmainham Gaol, and from there taken to the gaol, where he is to be executed.
Connolly has been so badly injured from the fighting that he is unable to stand before the firing squad. He is carried to a prison courtyard on a stretcher. Instead of being marched to the same spot where the others had been executed, at the far end of the execution yard, he is tied to a chair and then shot.
His body, along with those of the other leaders, is put in a mass grave without a coffin. The executions of the rebel leaders deeply angers the majority of the Irish population, most of whom had shown no support during the rebellion. It is Connolly’s execution that causes the most controversy. The executions are not well received, even throughout Britain, and draw unwanted attention from the United States, which the British Government is seeking to bring into the war in Europe. Prime Minister H. H. Asquith orders that no more executions are to take place, an exception being that of Roger Casement as he has not yet been tried.