Around this time, his father became an activist in the Irish Transport and General Workers' Union, playing a part in the Dublin lock-out of 1913, which was an important influence on Seán.

Over the next two days, McLoughlin repeatedly travelled between the Institution and General Post Office (GPO), updating the leadership on progress and obtaining supplies.

Once there, James Connolly gave him command of thirty volunteers and a mission to occupy the offices of the Irish Independent, to maintain a watch on British troop movements and potentially bombard them, if they began an assault.

He successfully evacuated 300 men to Moore Street, and this led Connolly and the other headquarters staff to award him the title of commandant-general and overall charge of the Volunteers' military operations, even though he was still only 21 years old.

He planned a break-out, hoping to surprise the British and win against them in hand-to-hand combat, but the commander-in-chief, Patrick Pearse decided that the risk of civilian casualties was too high, and instead surrendered.

After a short return to Scotland to complete some planned public speeches, he spent several more months in Dublin, trying to build the Communist Labour Party, while still active in the Volunteers.

In November, he began another speaking tour of Britain, starting in Sheffield, where he contacted local Irish emigrants and helped arrange the smuggling of arms to the Volunteers.

[5][6] He began speaking at unemployed workers' events and associated himself with the newly founded Communist Party of Ireland (CPI), which was led by his old comrade Roddy Connolly.

In line with the CPI's strategy, he joined the Irish Republican Army (IRA) to fight on the anti-treaty side in the Civil War, and was given command of a column in County Cork.