Russell was interned along with Ernie O'Malley (the assistant chief of staff of the Anti-Treaty IRA during the Irish Civil War) in the Curragh Camp and was released on 17 July 1924, well over a year after the end of hostilities.

During his imprisonment he undertook a 41 day hunger strike[8][2] In 1925, after the civil war, he was jailed in Mountjoy Prison but escaped on 25 November in a breakout he helped organise.

[2] He met Éamon de Valera, President of the Executive Council of the Irish Free State at Government Buildings during 1934, to discuss potentially uniting the IRA and Fianna Fáil.

[2][10] In return for political support, De Valera asked for the IRA to lay down their arms and cease any overt actions.

Russell was open to the idea, but would only agree to IRA inactivity for 5 years, believing that sufficient time for Fianna Fáil to declare an outright Irish Republic.

Following Russell's election, Tom Barry, John Joe Sheehy, and Tomás Óg MacCurtain immediately resigned from the IRA, with Barry denouncing Russell's planned bombing campaign as "doomed to failure as the Fenian dynamite campaign" and "unethical and immoral",[10] while subsequently, more conservative Republicans such as Patrick McGrath and Seamus O'Donovan returned to the fold.

[2] Barry would later claim that Russell and his supporters had said that the German American Bund would fund their planned attack on the United Kingdom.

Seven of these former TDs transferred what authority they believed they had as representatives of the second Dáil to the IRA army council, thus, in their minds, rendering it the legitimate governing body of Ireland.

He was trailed by Federal Bureau of Investigation "G-Men" at the request of Scotland Yard, and then detained by the United States Immigration Service at the Detroit border with Windsor, Ontario[16] during the American visit of King George VI.

[17] While in the United States, Russell met with his Clan na Gael host Joseph McGarrity and Robert Monteith, one of Casement's colleagues in 1916 and, at that time, director of Father Charles Coughlin's National Union for Social Justice.

Anxious to skip his bail, which expired on 16 April, Russell made contact, through the offices of McGarrity, with German agent 'V-Rex', also known as Carl Rekowski.

[citation needed] Accorded the privileges of a diplomat and provided with a villa and a chauffeur-driven car, Russell's liaison officer while in Nazi Germany was SS-Standartenführer Edmund Veesenmayer.

As he received explosives training, his return to Ireland with a definite sabotage objective was planned by German Army Intelligence.

[citation needed] On 15 July 1940, Frank Ryan – an IRA man who had fought on the Republican side in the Spanish Civil War and was captured by Franco forces – was handed over to the Abwehr and taken to Germany.

The capture of the German agents from Operation Lobster I did not prevent Abwehr Chief Wilhelm Canaris sanctioning the transport of Russell to Ireland.

A number of conspiracy theories arose around the subject of Russell's death, including that he was poisoned on board the ship, shot by the British Secret Service in France, or murdered by Kurt Haller.

[11] Historian Caoimhe Nic Dhaibheid states that Russell's motivation was to obtain arms and money from Germany to further Irish republican aims.

The same rally was also addressed by then Provisional IRA Army Council member Brian Keenan who said: I don't know what was in the depth of Seán Russell's thinking down the years, but I am sure he was never far from Pearse's own position, who said, as a patriot, preferring death to slavery, I know no other way.

[34] In 2020, McDonald was retroactively criticised for her attendance at the rally by Taoiseach Micheál Martin, who stated "The idea someone was working with the Nazis to undermine Britain when Europe was in great peril and [that] he should be commemorated is something that Sinn Féin need a wake-up call on" as well as adding that he thought Russell was "wrong" and that "collaborating with the Nazis should not be condoned in any way".

[35] In 2022, politician and journalist Shane Ross condemned Russell as one of "the most unsavoury supporters of terrorism in the history of the republican movement".

A statement issued to the press in justification of the vandalism read (verbatim): Six million Jews, thousands of political dissidents, homosexuals, Roma people, Soviet prisoners of war and the disabled were put to death by the fascist hate machine that overran and terrified Europe from 1939 to 45.

Sean Russell was one of many nationalist fanatics who looked to Hitler for political and military support in the IRA's quest to reunify Ireland at the point of the bayonets of the Gestapo.

At the Wannsee Conference, the infamous Nazi gathering that planned the "Final Solution", the Jewish community in Ireland was marked down for annihilation.

Having freed Ireland from British rule, the Nazis expected their collaborators to help them round up Dublin's Jews and ship them off to Auschwitz.