Politically, Ó Cadhain was an Irish republican and anti-clerical Marxist, who promoted the Athghabháil na hÉireann ("Re-Conquest of Ireland"), (meaning both decolonization and re-Gaelicisation).

[3] During this period, he also participated in the land campaign of native speakers, which led to the establishment of the Ráth Cairn neo-Gaeltacht in County Meath.

Subsequently, he was arrested and interned during the Emergency (the second world war period in Ireland) on the Curragh Camp in County Kildare, due to his continued involvement in the IRA.

As a writer, Ó Cadhain is acknowledged to be a major part of the revival of modernist literature in the Irish, where it had been largely dormant since the execution of Patrick Pearse in 1916.

Consequently, much of what Ó Cadhain wrote is, like the poetry of fellow linguistic experimentalist Liam S. Gógan, reputedly very hard to understand for a non-native speaker.

He translated Charles Kickham's novel Sally Kavanagh into Irish as Saile Chaomhánach, nó na hUaigheanna Folmha.

His political views can most easily be discerned in a small book about the development of Irish nationalism and radicalism[5] since Theobald Wolfe Tone, Tone Inné agus Inniu; and in the beginning of the sixties, he wrote – partly in Irish, partly in English – a comprehensive survey of the social status and actual use of the language in the west of Ireland, published as An Ghaeilge Bheo – Destined to Pass.

[6] Ó Cadhain had frequent difficulties getting his work edited, but unpublished writings have appeared at least every two years since the publication of Athnuachan in the mid-nineties.

While living in Camus, County Galway (an Irish-speaking Gaeltacht village) he resided with Seosamh Mac Mathúna, who had been a member of the IRA since 1918.

At the onset of the Troubles in Northern Ireland, he welcomed resistance to British rule as well as the idea of an armed struggle, and once again stated his Marxist outlook on the situation; "capitalism must go as well as the Border".

Misneach used civil disobedience tactics influenced by Saunders Lewis, the Welsh language advocate and founder of Plaid Cymru.