O’Sullivan, then 25, was the youngest IRB officer fighting in the GPO (three months younger than his cousin Michael Collins). He had been personally chosen by leader Seán Mac Diarmada to serve as his aide-de-camp.

He was an Irish teacher, Irish language scholar, army officer, barrister and Sinn Féin and Fine Gael politician. Following the Rising, he was interned in Frongoch in Wales with Collins and others who, unlike the rebellion’s leaders such as Pearse and Mac Diarmada, escaped execution. It was here that O’Sullivan’s and Collins’ friendship grew into a strong bond that would last until Collins’ death in August 1922.

O’Sullivan died on Good Friday (25 March) 1948, aged 57, and received a state funeral on the following Easter Monday – exactly 32 years after the Easter Rising. Thousands of people lined the streets of Dublin to watch as a horse-drawn carriage carried his coffin, draped in the same Tricolour that had covered Collins’ coffin a quarter-century earlier, past the GPO and other landmarks to his final resting place at Glasnevin Cemetery.

In O’Sullivan’s obituary appearing in the Irish Independent, an individual describing himself as ‘a colleague’ wrote of O’Sullivan’s contributions to Ireland following 1916:

‘When the jails and prison camps opened Gearoid came back to resume the struggle. At a critical moment and at the instance of Michael Collins, he was summoned to an honourable, if highly dangerous, post – to replace Collins as Adjutant-General of the Volunteers. In the stern years that followed there was no braver heart or cooler head in the councils of the nation’s army. From his dingy office, within a stone’s throw of Dublin Castle, surrounded by excursions and alarms, meeting places where plans for action were settled, and thence to an uneasy rest.’

Image: Declan Kerr – Irish Artist