In May 1918, along with Éamon de Valera and 72 other Sinn Féiners, Griffith was arrested on the pretext of involvement in the fictitious German Plot.
Griffith spent ten months interned in Gloucester jail, being released on 6 March 1919.
Fr.
O'Flanagan was left as Acting-President of Sinn Féin.
 Griffith was put forward as a Sinn Féin candidate for the East Cavan by-election on 20 June 1918.
Under the slogan "Put him in to get him out," and was elected.
and held the seat when Sinn Féin subsequently routed the Irish Parliamentary Party at the 1918 general election with a commitment of abstentionism from the British House of Commons.
Griffith was returned for  returned for both East Cavan and Tyrone North West.

Sinn Féin's MPs set up an Irish parliament, Dáil Éireann and declared independence for the Irish Republic; the Irish War of Independence followed almost immediately.
The dominant leaders in the Dáil included Éamon de Valera, President of Dáil Éireann (1919–21), President of the Republic (1921–1922), and Michael Collins, Minister for Finance, head of the IRB and the Irish Republican Army's Director of Intelligence.

During de Valera's absence in the United States (1919–21) Griffith served as Acting President and gave regular press interviews.
He was arrested at his house at 3am, on 26 November 1920, and later jailed, Fr.
O'Flanagan again taking over as acting leader until de Valera returned from America on 23 December.
Griffith was to spend the next seven months in Dublin's Mountjoy Prison.
He was released on 30 June 1921 as peace moves got under way.

In Ireland, a general election was held on 24 May 1921 and Griffith, while still in prison, headed the poll in the contested constituency of Fermanagh and Tyrone, and was returned unopposed for Cavan.
On 26 August 1921, Griffith was appointed Minister for Foreign Affairs in the new Irish cabinet.
In May 1918, along with Éamon de Valera and 72 other Sinn Féiners, Griffith was arrested on the pretext of involvement in the fictitious German Plot. Griffith spent ten months interned in Gloucester jail, being released on 6 March 1919. Fr. O'Flanagan was left as Acting-President of Sinn Féin.  Griffith was put forward as a Sinn Féin candidate for the East Cavan by-election on 20 June 1918. Under the slogan "Put him in to get him out," and was elected. and held the seat when Sinn Féin subsequently routed the Irish Parliamentary Party at the 1918 general election with a commitment of abstentionism from the British House of Commons. Griffith was returned for  returned for both East Cavan and Tyrone North West.
Sinn Féin's MPs set up an Irish parliament, Dáil Éireann and declared independence for the Irish Republic; the Irish War of Independence followed almost immediately. The dominant leaders in the Dáil included Éamon de Valera, President of Dáil Éireann (1919–21), President of the Republic (1921–1922), and Michael Collins, Minister for Finance, head of the IRB and the Irish Republican Army's Director of Intelligence.
During de Valera's absence in the United States (1919–21) Griffith served as Acting President and gave regular press interviews. He was arrested at his house at 3am, on 26 November 1920, and later jailed, Fr. O'Flanagan again taking over as acting leader until de Valera returned from America on 23 December. Griffith was to spend the next seven months in Dublin's Mountjoy Prison. He was released on 30 June 1921 as peace moves got under way.
In Ireland, a general election was held on 24 May 1921 and Griffith, while still in prison, headed the poll in the contested constituency of Fermanagh and Tyrone, and was returned unopposed for Cavan. On 26 August 1921, Griffith was appointed Minister for Foreign Affairs in the new Irish cabinet.
Arthur Griffith